diff --git a/lexers/c/cql.go b/lexers/c/cql.go
index 1126916..0d460b9 100644
--- a/lexers/c/cql.go
+++ b/lexers/c/cql.go
@@ -23,6 +23,15 @@ var CassandraCQL = internal.Register(MustNewLexer(
 			{`(ascii|bigint|blob|boolean|counter|date|decimal|double|float|frozen|inet|int|list|map|set|smallint|text|time|timestamp|timeuuid|tinyint|tuple|uuid|varchar|varint)\b`, NameBuiltin, nil},
 			{Words(``, `\b`, `ADD`, `AGGREGATE`, `ALL`, `ALLOW`, `ALTER`, `AND`, `ANY`, `APPLY`, `AS`, `ASC`, `AUTHORIZE`, `BATCH`, `BEGIN`, `BY`, `CLUSTERING`, `COLUMNFAMILY`, `COMPACT`, `CONSISTENCY`, `COUNT`, `CREATE`, `CUSTOM`, `DELETE`, `DESC`, `DISTINCT`, `DROP`, `EACH_QUORUM`, `ENTRIES`, `EXISTS`, `FILTERING`, `FROM`, `FULL`, `GRANT`, `IF`, `IN`, `INDEX`, `INFINITY`, `INSERT`, `INTO`, `KEY`, `KEYS`, `KEYSPACE`, `KEYSPACES`, `LEVEL`, `LIMIT`, `LOCAL_ONE`, `LOCAL_QUORUM`, `MATERIALIZED`, `MODIFY`, `NAN`, `NORECURSIVE`, `NOSUPERUSER`, `NOT`, `OF`, `ON`, `ONE`, `ORDER`, `PARTITION`, `PASSWORD`, `PER`, `PERMISSION`, `PERMISSIONS`, `PRIMARY`, `QUORUM`, `RENAME`, `REVOKE`, `SCHEMA`, `SELECT`, `STATIC`, `STORAGE`, `SUPERUSER`, `TABLE`, `THREE`, `TO`, `TOKEN`, `TRUNCATE`, `TTL`, `TWO`, `TYPE`, `UNLOGGED`, `UPDATE`, `USE`, `USER`, `USERS`, `USING`, `VALUES`, `VIEW`, `WHERE`, `WITH`, `WRITETIME`, `REPLICATION`, `OR`, `REPLACE`, `FUNCTION`, `CALLED`, `INPUT`, `RETURNS`, `LANGUAGE`, `ROLE`, `ROLES`, `TRIGGER`, `DURABLE_WRITES`, `LOGIN`, `OPTIONS`, `LOGGED`, `SFUNC`, `STYPE`, `FINALFUNC`, `INITCOND`, `IS`, `CONTAINS`, `JSON`, `PAGING`, `OFF`), Keyword, nil},
 			{"[+*/<>=~!@#%^&|`?-]+", Operator, nil},
+			{`(?s)(java|javascript)(\s+)(AS)(\s+)('|\$\$)(.*?)(\5)`,
+				UsingByGroup(
+					internal.Get,
+					1, 6,
+					NameBuiltin, TextWhitespace, Keyword, TextWhitespace,
+					LiteralStringHeredoc, LiteralStringHeredoc, LiteralStringHeredoc,
+				),
+				nil,
+			},
 			{`(true|false|null)\b`, KeywordConstant, nil},
 			{`0x[0-9a-f]+`, LiteralNumberHex, nil},
 			{`[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}`, LiteralNumberHex, nil},
diff --git a/lexers/m/markdown.go b/lexers/m/markdown.go
index 753f986..b4690e3 100644
--- a/lexers/m/markdown.go
+++ b/lexers/m/markdown.go
@@ -21,8 +21,15 @@ var Markdown = internal.Register(MustNewLexer(
 			{`^(\s*)([*-])(\s)(.+\n)`, ByGroups(Text, Keyword, Text, UsingSelf("inline")), nil},
 			{`^(\s*)([0-9]+\.)( .+\n)`, ByGroups(Text, Keyword, UsingSelf("inline")), nil},
 			{`^(\s*>\s)(.+\n)`, ByGroups(Keyword, GenericEmph), nil},
-			{"^(```\\n)([\\w\\W]*?)(^```$)", ByGroups(LiteralString, Text, LiteralString), nil},
-			{"^(```)(\\w+)(\\n)([\\w\\W]*?)(^```$)", EmitterFunc(markdownCodeBlock), nil},
+			{"^(```\\n)([\\w\\W]*?)(^```$)", ByGroups(String, Text, String), nil},
+			{"^(```)(\\w+)(\\n)([\\w\\W]*?)(^```$)",
+				UsingByGroup(
+					internal.Get,
+					2, 4,
+					String, String, String, Text, String,
+				),
+				nil,
+			},
 			Include("inline"),
 		},
 		"inline": {
@@ -38,26 +45,3 @@ var Markdown = internal.Register(MustNewLexer(
 		},
 	},
 ))
-
-func markdownCodeBlock(groups []string, lexer Lexer) Iterator {
-	iterators := []Iterator{}
-	tokens := []*Token{
-		{String, groups[1]},
-		{String, groups[2]},
-		{Text, groups[3]},
-	}
-	code := groups[4]
-	lexer = internal.Get(groups[2])
-	if lexer == nil {
-		tokens = append(tokens, &Token{String, code})
-		iterators = append(iterators, Literator(tokens...))
-	} else {
-		sub, err := lexer.Tokenise(nil, code)
-		if err != nil {
-			panic(err)
-		}
-		iterators = append(iterators, Literator(tokens...), sub)
-	}
-	iterators = append(iterators, Literator(&Token{String, groups[5]}))
-	return Concaterator(iterators...)
-}
diff --git a/lexers/p/postgres.go b/lexers/p/postgres.go
index 3564330..3afa54d 100644
--- a/lexers/p/postgres.go
+++ b/lexers/p/postgres.go
@@ -21,6 +21,18 @@ var PostgreSQL = internal.Register(MustNewLexer(
 			{`--.*\n?`, CommentSingle, nil},
 			{`/\*`, CommentMultiline, Push("multiline-comments")},
 			{`(bigint|bigserial|bit|bit\s+varying|bool|boolean|box|bytea|char|character|character\s+varying|cidr|circle|date|decimal|double\s+precision|float4|float8|inet|int|int2|int4|int8|integer|interval|json|jsonb|line|lseg|macaddr|money|numeric|path|pg_lsn|point|polygon|real|serial|serial2|serial4|serial8|smallint|smallserial|text|time|timestamp|timestamptz|timetz|tsquery|tsvector|txid_snapshot|uuid|varbit|varchar|with\s+time\s+zone|without\s+time\s+zone|xml|anyarray|anyelement|anyenum|anynonarray|anyrange|cstring|fdw_handler|internal|language_handler|opaque|record|void)\b`, NameBuiltin, nil},
+			{`(?s)(DO)(\s+)(?:(LANGUAGE)?(\s+)('?)(\w+)?('?)(\s+))?(\$)([^$]*)(\$)(.*?)(\$)(\10)(\$)`,
+				UsingByGroup(
+					internal.Get,
+					6, 12,
+					Keyword, Text, Keyword, Text, // DO LANGUAGE
+					StringSingle, StringSingle, StringSingle, Text, // 'plpgsql'
+					StringHeredoc, StringHeredoc, StringHeredoc, // $tag$
+					StringHeredoc,                               // (code block)
+					StringHeredoc, StringHeredoc, StringHeredoc, // $tag$
+				),
+				nil,
+			},
 			{Words(``, `\b`, `ABORT`, `ABSOLUTE`, `ACCESS`, `ACTION`, `ADD`, `ADMIN`, `AFTER`, `AGGREGATE`, `ALL`, `ALSO`, `ALTER`, `ALWAYS`, `ANALYSE`, `ANALYZE`, `AND`, `ANY`, `ARRAY`, `AS`, `ASC`, `ASSERTION`, `ASSIGNMENT`, `ASYMMETRIC`, `AT`, `ATTRIBUTE`, `AUTHORIZATION`, `BACKWARD`, `BEFORE`, `BEGIN`, `BETWEEN`, `BIGINT`, `BINARY`, `BIT`, `BOOLEAN`, `BOTH`, `BY`, `CACHE`, `CALLED`, `CASCADE`, `CASCADED`, `CASE`, `CAST`, `CATALOG`, `CHAIN`, `CHAR`, `CHARACTER`, `CHARACTERISTICS`, `CHECK`, `CHECKPOINT`, `CLASS`, `CLOSE`, `CLUSTER`, `COALESCE`, `COLLATE`, `COLLATION`, `COLUMN`, `COMMENT`, `COMMENTS`, `COMMIT`, `COMMITTED`, `CONCURRENTLY`, `CONFIGURATION`, `CONNECTION`, `CONSTRAINT`, `CONSTRAINTS`, `CONTENT`, `CONTINUE`, `CONVERSION`, `COPY`, `COST`, `CREATE`, `CROSS`, `CSV`, `CURRENT`, `CURRENT_CATALOG`, `CURRENT_DATE`, `CURRENT_ROLE`, `CURRENT_SCHEMA`, `CURRENT_TIME`, `CURRENT_TIMESTAMP`, `CURRENT_USER`, `CURSOR`, `CYCLE`, `DATA`, `DATABASE`, `DAY`, `DEALLOCATE`, `DEC`, `DECIMAL`, `DECLARE`, `DEFAULT`, `DEFAULTS`, `DEFERRABLE`, `DEFERRED`, `DEFINER`, `DELETE`, `DELIMITER`, `DELIMITERS`, `DESC`, `DICTIONARY`, `DISABLE`, `DISCARD`, `DISTINCT`, `DO`, `DOCUMENT`, `DOMAIN`, `DOUBLE`, `DROP`, `EACH`, `ELSE`, `ENABLE`, `ENCODING`, `ENCRYPTED`, `END`, `ENUM`, `ESCAPE`, `EVENT`, `EXCEPT`, `EXCLUDE`, `EXCLUDING`, `EXCLUSIVE`, `EXECUTE`, `EXISTS`, `EXPLAIN`, `EXTENSION`, `EXTERNAL`, `EXTRACT`, `FALSE`, `FAMILY`, `FETCH`, `FILTER`, `FIRST`, `FLOAT`, `FOLLOWING`, `FOR`, `FORCE`, `FOREIGN`, `FORWARD`, `FREEZE`, `FROM`, `FULL`, `FUNCTION`, `FUNCTIONS`, `GLOBAL`, `GRANT`, `GRANTED`, `GREATEST`, `GROUP`, `HANDLER`, `HAVING`, `HEADER`, `HOLD`, `HOUR`, `IDENTITY`, `IF`, `ILIKE`, `IMMEDIATE`, `IMMUTABLE`, `IMPLICIT`, `IN`, `INCLUDING`, `INCREMENT`, `INDEX`, `INDEXES`, `INHERIT`, `INHERITS`, `INITIALLY`, `INLINE`, `INNER`, `INOUT`, `INPUT`, `INSENSITIVE`, `INSERT`, `INSTEAD`, `INT`, `INTEGER`, `INTERSECT`, `INTERVAL`, `INTO`, `INVOKER`, `IS`, `ISNULL`, `ISOLATION`, `JOIN`, `KEY`, `LABEL`, `LANGUAGE`, `LARGE`, `LAST`, `LATERAL`, `LC_COLLATE`, `LC_CTYPE`, `LEADING`, `LEAKPROOF`, `LEAST`, `LEFT`, `LEVEL`, `LIKE`, `LIMIT`, `LISTEN`, `LOAD`, `LOCAL`, `LOCALTIME`, `LOCALTIMESTAMP`, `LOCATION`, `LOCK`, `MAPPING`, `MATCH`, `MATERIALIZED`, `MAXVALUE`, `MINUTE`, `MINVALUE`, `MODE`, `MONTH`, `MOVE`, `NAME`, `NAMES`, `NATIONAL`, `NATURAL`, `NCHAR`, `NEXT`, `NO`, `NONE`, `NOT`, `NOTHING`, `NOTIFY`, `NOTNULL`, `NOWAIT`, `NULL`, `NULLIF`, `NULLS`, `NUMERIC`, `OBJECT`, `OF`, `OFF`, `OFFSET`, `OIDS`, `ON`, `ONLY`, `OPERATOR`, `OPTION`, `OPTIONS`, `OR`, `ORDER`, `ORDINALITY`, `OUT`, `OUTER`, `OVER`, `OVERLAPS`, `OVERLAY`, `OWNED`, `OWNER`, `PARSER`, `PARTIAL`, `PARTITION`, `PASSING`, `PASSWORD`, `PLACING`, `PLANS`, `POLICY`, `POSITION`, `PRECEDING`, `PRECISION`, `PREPARE`, `PREPARED`, `PRESERVE`, `PRIMARY`, `PRIOR`, `PRIVILEGES`, `PROCEDURAL`, `PROCEDURE`, `PROGRAM`, `QUOTE`, `RANGE`, `READ`, `REAL`, `REASSIGN`, `RECHECK`, `RECURSIVE`, `REF`, `REFERENCES`, `REFRESH`, `REINDEX`, `RELATIVE`, `RELEASE`, `RENAME`, `REPEATABLE`, `REPLACE`, `REPLICA`, `RESET`, `RESTART`, `RESTRICT`, `RETURNING`, `RETURNS`, `REVOKE`, `RIGHT`, `ROLE`, `ROLLBACK`, `ROW`, `ROWS`, `RULE`, `SAVEPOINT`, `SCHEMA`, `SCROLL`, `SEARCH`, `SECOND`, `SECURITY`, `SELECT`, `SEQUENCE`, `SEQUENCES`, `SERIALIZABLE`, `SERVER`, `SESSION`, `SESSION_USER`, `SET`, `SETOF`, `SHARE`, `SHOW`, `SIMILAR`, `SIMPLE`, `SMALLINT`, `SNAPSHOT`, `SOME`, `STABLE`, `STANDALONE`, `START`, `STATEMENT`, `STATISTICS`, `STDIN`, `STDOUT`, `STORAGE`, `STRICT`, `STRIP`, `SUBSTRING`, `SYMMETRIC`, `SYSID`, `SYSTEM`, `TABLE`, `TABLES`, `TABLESPACE`, `TEMP`, `TEMPLATE`, `TEMPORARY`, `TEXT`, `THEN`, `TIME`, `TIMESTAMP`, `TO`, `TRAILING`, `TRANSACTION`, `TREAT`, `TRIGGER`, `TRIM`, `TRUE`, `TRUNCATE`, `TRUSTED`, `TYPE`, `TYPES`, `UNBOUNDED`, `UNCOMMITTED`, `UNENCRYPTED`, `UNION`, `UNIQUE`, `UNKNOWN`, `UNLISTEN`, `UNLOGGED`, `UNTIL`, `UPDATE`, `USER`, `USING`, `VACUUM`, `VALID`, `VALIDATE`, `VALIDATOR`, `VALUE`, `VALUES`, `VARCHAR`, `VARIADIC`, `VARYING`, `VERBOSE`, `VERSION`, `VIEW`, `VIEWS`, `VOLATILE`, `WHEN`, `WHERE`, `WHITESPACE`, `WINDOW`, `WITH`, `WITHIN`, `WITHOUT`, `WORK`, `WRAPPER`, `WRITE`, `XML`, `XMLATTRIBUTES`, `XMLCONCAT`, `XMLELEMENT`, `XMLEXISTS`, `XMLFOREST`, `XMLPARSE`, `XMLPI`, `XMLROOT`, `XMLSERIALIZE`, `YEAR`, `YES`, `ZONE`), Keyword, nil},
 			{"[+*/<>=~!@#%^&|`?-]+", Operator, nil},
 			{`::`, Operator, nil},
@@ -29,7 +41,18 @@ var PostgreSQL = internal.Register(MustNewLexer(
 			{`[0-9]+`, LiteralNumberInteger, nil},
 			{`((?:E|U&)?)(')`, ByGroups(LiteralStringAffix, LiteralStringSingle), Push("string")},
 			{`((?:U&)?)(")`, ByGroups(LiteralStringAffix, LiteralStringName), Push("quoted-ident")},
-			// { `(?s)(\$)([^$]*)(\$)(.*?)(\$)(\2)(\$)`, ?? <function language_callback at 0x101105400> ??, nil },
+			{`(?s)(\$)([^$]*)(\$)(.*?)(\$)(\2)(\$)(\s+)(LANGUAGE)?(\s+)('?)(\w+)?('?)`,
+				UsingByGroup(internal.Get,
+					12, 4,
+					StringHeredoc, StringHeredoc, StringHeredoc, // $tag$
+					StringHeredoc,                               // (code block)
+					StringHeredoc, StringHeredoc, StringHeredoc, // $tag$
+					Text, Keyword, Text, // <space> LANGUAGE <space>
+					StringSingle, StringSingle, StringSingle, // 'type'
+				),
+				nil,
+			},
+			{`(?s)(\$)([^$]*)(\$)(.*?)(\$)(\2)(\$)`, LiteralStringHeredoc, nil},
 			{`[a-z_]\w*`, Name, nil},
 			{`:(['"]?)[a-z]\w*\b\1`, NameVariable, nil},
 			{`[;:()\[\]{},.]`, Punctuation, nil},
diff --git a/lexers/testdata/cql.actual b/lexers/testdata/cql.actual
index 7925ecb..727171d 100644
--- a/lexers/testdata/cql.actual
+++ b/lexers/testdata/cql.actual
@@ -54,3 +54,15 @@ CREATE MATERIALIZED VIEW cyclist_by_country AS SELECT age, birthday, name, count
 CREATE MATERIALIZED VIEW cyclist_by_birthday AS SELECT age, birthday, name, country FROM cyclist_mv WHERE birthday is NOT NULL AND cid IS NOT NULL PRIMARY KEY (birthday, cid);
 DROP MATERIALIZED VIEW cyclist_by_age;
 INSERT INTO cycling.calendar (race_id, race_name, race_start_date, race_end_date) VALUES (200, 'placeholder', '2015-05-27', '2015-05-27') USING TIMESTAMP 123456789;
+
+CREATE FUNCTION IF NOT EXISTS cycling.left (column TEXT,num int)
+RETURNS NULL ON NULL INPUT
+RETURNS text
+LANGUAGE javascript AS $$ 
+  column.substring(0,num) 
+$$;
+
+CREATE OR REPLACE FUNCTION cycling.fLog (input double)
+CALLED ON NULL INPUT
+RETURNS double LANGUAGE java AS
+'return Double.valueOf(Math.log(input.doubleValue()));';
diff --git a/lexers/testdata/cql.expected b/lexers/testdata/cql.expected
index 17da6ba..bc5f849 100644
--- a/lexers/testdata/cql.expected
+++ b/lexers/testdata/cql.expected
@@ -969,5 +969,117 @@
   {"type":"TextWhitespace","value":" "},
   {"type":"LiteralNumberFloat","value":"123456789"},
   {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"FUNCTION"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"NOT"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"EXISTS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"cycling"},
+  {"type":"Punctuation","value":"."},
+  {"type":"Name","value":"left"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"("},
+  {"type":"Name","value":"column"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"TEXT"},
+  {"type":"Punctuation","value":","},
+  {"type":"Name","value":"num"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"int"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordConstant","value":"NULL"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"ON"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordConstant","value":"NULL"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"INPUT"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"text"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"LANGUAGE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"javascript"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"AS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"LiteralStringHeredoc","value":"$$"},
+  {"type":"Text","value":" \n  "},
+  {"type":"NameOther","value":"column"},
+  {"type":"Punctuation","value":"."},
+  {"type":"NameOther","value":"substring"},
+  {"type":"Punctuation","value":"("},
+  {"type":"LiteralNumberInteger","value":"0"},
+  {"type":"Punctuation","value":","},
+  {"type":"NameOther","value":"num"},
+  {"type":"Punctuation","value":")"},
+  {"type":"Text","value":" \n"},
+  {"type":"LiteralStringHeredoc","value":"$$"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"OR"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"REPLACE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"FUNCTION"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"cycling"},
+  {"type":"Punctuation","value":"."},
+  {"type":"Name","value":"fLog"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"("},
+  {"type":"Keyword","value":"input"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"double"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"CALLED"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"ON"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordConstant","value":"NULL"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"INPUT"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"double"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"LANGUAGE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"java"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"AS"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"LiteralStringHeredoc","value":"'"},
+  {"type":"Keyword","value":"return"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"Double"},
+  {"type":"Operator","value":"."},
+  {"type":"NameAttribute","value":"valueOf"},
+  {"type":"Operator","value":"("},
+  {"type":"Name","value":"Math"},
+  {"type":"Operator","value":"."},
+  {"type":"NameAttribute","value":"log"},
+  {"type":"Operator","value":"("},
+  {"type":"Name","value":"input"},
+  {"type":"Operator","value":"."},
+  {"type":"NameAttribute","value":"doubleValue"},
+  {"type":"Operator","value":"()));"},
+  {"type":"LiteralStringHeredoc","value":"'"},
+  {"type":"Punctuation","value":";"},
   {"type":"TextWhitespace","value":"\n"}
 ]
diff --git a/lexers/testdata/markdown.actual b/lexers/testdata/markdown.actual
new file mode 100644
index 0000000..3fc0a50
--- /dev/null
+++ b/lexers/testdata/markdown.actual
@@ -0,0 +1,81 @@
+# about
+
+## user defined function in cql
+
+```javascript
+  column.substring(0,num) 
+```
+
+```cql
+CREATE FUNCTION IF NOT EXISTS cycling.left (column TEXT,num int)
+RETURNS NULL ON NULL INPUT
+RETURNS text
+LANGUAGE javascript AS $$ 
+  column.substring(0,num) 
+$$;
+
+CREATE OR REPLACE FUNCTION cycling.fLog (input double)
+CALLED ON NULL INPUT
+RETURNS double LANGUAGE java AS
+'return Double.valueOf(Math.log(input.doubleValue()));';
+```
+
+```postgres
+DROP TABLE IF EXISTS emp CASCADE;
+
+CREATE TABLE emp (
+  empname text,
+  salary integer,
+  last_date timestamp,
+  last_user text
+);
+
+select 
+  $my_tag$aoeuaoeu$my_tag$ as blah
+;
+
+CREATE OR REPLACE FUNCTION emp_stamp() RETURNS trigger AS $emp_stamp$
+BEGIN
+  -- Check that empname and salary are given
+  IF NEW.empname IS NULL THEN
+    RAISE EXCEPTION 'empname cannot be null';
+  END IF;
+  IF NEW.salary IS NULL THEN
+    RAISE EXCEPTION '% cannot have null salary', NEW.empname;
+  END IF;
+
+  -- Who works for us when she must pay for it?
+  IF NEW.salary < 0 THEN
+    RAISE EXCEPTION '% cannot have a negative salary', NEW.empname;
+  END IF;
+
+  -- Remember who changed the payroll when
+  NEW.last_date := current_timestamp;
+  NEW.last_user := current_user;
+  RETURN NEW;
+END;
+$emp_stamp$ LANGUAGE plpgsql;
+
+CREATE TRIGGER emp_stamp BEFORE INSERT OR UPDATE ON emp
+  FOR EACH ROW EXECUTE PROCEDURE emp_stamp();
+
+DO language plpgsql $$
+declare r record;
+begin
+  for r in select * from books
+loop
+  execute 'select ''' || r.title || '''';
+end loop;
+end
+$$;
+
+DO $$
+declare r record;
+begin
+  for r in select * from books
+loop
+  execute 'select ''' || r.title || '''';
+end loop;
+end
+$$;
+```
diff --git a/lexers/testdata/markdown.expected b/lexers/testdata/markdown.expected
new file mode 100644
index 0000000..2b5aa84
--- /dev/null
+++ b/lexers/testdata/markdown.expected
@@ -0,0 +1,427 @@
+[
+  {"type":"GenericHeading","value":"#"},
+  {"type":"Text","value":" about\n"},
+  {"type":"Error","value":"\n"},
+  {"type":"GenericSubheading","value":"##"},
+  {"type":"Text","value":" user defined function in cql\n"},
+  {"type":"Error","value":"\n"},
+  {"type":"LiteralString","value":"```javascript\n"},
+  {"type":"Text","value":"  "},
+  {"type":"NameOther","value":"column"},
+  {"type":"Punctuation","value":"."},
+  {"type":"NameOther","value":"substring"},
+  {"type":"Punctuation","value":"("},
+  {"type":"LiteralNumberInteger","value":"0"},
+  {"type":"Punctuation","value":","},
+  {"type":"NameOther","value":"num"},
+  {"type":"Punctuation","value":")"},
+  {"type":"Text","value":" \n"},
+  {"type":"LiteralString","value":"```"},
+  {"type":"Error","value":"\n\n"},
+  {"type":"LiteralString","value":"```cql\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"FUNCTION"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"NOT"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"EXISTS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"cycling"},
+  {"type":"Punctuation","value":"."},
+  {"type":"Name","value":"left"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"("},
+  {"type":"Name","value":"column"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"TEXT"},
+  {"type":"Punctuation","value":","},
+  {"type":"Name","value":"num"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"int"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordConstant","value":"NULL"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"ON"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordConstant","value":"NULL"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"INPUT"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"text"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"LANGUAGE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"javascript"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"AS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"LiteralStringHeredoc","value":"$$"},
+  {"type":"Text","value":" \n  "},
+  {"type":"NameOther","value":"column"},
+  {"type":"Punctuation","value":"."},
+  {"type":"NameOther","value":"substring"},
+  {"type":"Punctuation","value":"("},
+  {"type":"LiteralNumberInteger","value":"0"},
+  {"type":"Punctuation","value":","},
+  {"type":"NameOther","value":"num"},
+  {"type":"Punctuation","value":")"},
+  {"type":"Text","value":" \n"},
+  {"type":"LiteralStringHeredoc","value":"$$"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"OR"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"REPLACE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"FUNCTION"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"cycling"},
+  {"type":"Punctuation","value":"."},
+  {"type":"Name","value":"fLog"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"("},
+  {"type":"Keyword","value":"input"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"double"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"CALLED"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"ON"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordConstant","value":"NULL"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"INPUT"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"double"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"LANGUAGE"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"java"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"AS"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"LiteralStringHeredoc","value":"'"},
+  {"type":"Keyword","value":"return"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"Double"},
+  {"type":"Operator","value":"."},
+  {"type":"NameAttribute","value":"valueOf"},
+  {"type":"Operator","value":"("},
+  {"type":"Name","value":"Math"},
+  {"type":"Operator","value":"."},
+  {"type":"NameAttribute","value":"log"},
+  {"type":"Operator","value":"("},
+  {"type":"Name","value":"input"},
+  {"type":"Operator","value":"."},
+  {"type":"NameAttribute","value":"doubleValue"},
+  {"type":"Operator","value":"()));"},
+  {"type":"LiteralStringHeredoc","value":"'"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"LiteralString","value":"```"},
+  {"type":"Error","value":"\n\n"},
+  {"type":"LiteralString","value":"```postgres\n"},
+  {"type":"Keyword","value":"DROP"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"TABLE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"EXISTS"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"emp"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"CASCADE"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"TABLE"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"emp"},
+  {"type":"Text","value":" "},
+  {"type":"Punctuation","value":"("},
+  {"type":"Text","value":"\n  "},
+  {"type":"Name","value":"empname"},
+  {"type":"Text","value":" "},
+  {"type":"NameBuiltin","value":"text"},
+  {"type":"Punctuation","value":","},
+  {"type":"Text","value":"\n  "},
+  {"type":"Name","value":"salary"},
+  {"type":"Text","value":" "},
+  {"type":"NameBuiltin","value":"integer"},
+  {"type":"Punctuation","value":","},
+  {"type":"Text","value":"\n  "},
+  {"type":"Name","value":"last_date"},
+  {"type":"Text","value":" "},
+  {"type":"NameBuiltin","value":"timestamp"},
+  {"type":"Punctuation","value":","},
+  {"type":"Text","value":"\n  "},
+  {"type":"Name","value":"last_user"},
+  {"type":"Text","value":" "},
+  {"type":"NameBuiltin","value":"text"},
+  {"type":"Text","value":"\n"},
+  {"type":"Punctuation","value":");"},
+  {"type":"Text","value":"\n\n"},
+  {"type":"Keyword","value":"select"},
+  {"type":"Text","value":" \n  "},
+  {"type":"LiteralStringHeredoc","value":"$my_tag$aoeuaoeu$my_tag$"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"as"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"blah"},
+  {"type":"Text","value":"\n"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"OR"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"REPLACE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"FUNCTION"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"emp_stamp"},
+  {"type":"Punctuation","value":"()"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"RETURNS"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"trigger"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"AS"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringHeredoc","value":"$emp_stamp$"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"BEGIN"},
+  {"type":"Text","value":"\n  "},
+  {"type":"CommentSingle","value":"-- Check that empname and salary are given\n"},
+  {"type":"Text","value":"  "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"empname"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"IS"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"NULL"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"THEN"},
+  {"type":"Text","value":"\n    "},
+  {"type":"Keyword","value":"RAISE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"EXCEPTION"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"'empname cannot be null'"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"END"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"salary"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"IS"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"NULL"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"THEN"},
+  {"type":"Text","value":"\n    "},
+  {"type":"Keyword","value":"RAISE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"EXCEPTION"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"'% cannot have null salary'"},
+  {"type":"Punctuation","value":","},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"empname"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"END"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n\n  "},
+  {"type":"CommentSingle","value":"-- Who works for us when she must pay for it?\n"},
+  {"type":"Text","value":"  "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"salary"},
+  {"type":"Text","value":" "},
+  {"type":"Operator","value":"\u003c"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralNumberFloat","value":"0"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"THEN"},
+  {"type":"Text","value":"\n    "},
+  {"type":"Keyword","value":"RAISE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"EXCEPTION"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"'% cannot have a negative salary'"},
+  {"type":"Punctuation","value":","},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"empname"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"END"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"IF"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n\n  "},
+  {"type":"CommentSingle","value":"-- Remember who changed the payroll when\n"},
+  {"type":"Text","value":"  "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"last_date"},
+  {"type":"Text","value":" "},
+  {"type":"Operator","value":":="},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"current_timestamp"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Name","value":"NEW"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"last_user"},
+  {"type":"Text","value":" "},
+  {"type":"Operator","value":":="},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"current_user"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"RETURN"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"NEW"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"END"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n"},
+  {"type":"LiteralStringHeredoc","value":"$emp_stamp$"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"LANGUAGE"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"plpgsql"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n\n"},
+  {"type":"Keyword","value":"CREATE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"TRIGGER"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"emp_stamp"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"BEFORE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"INSERT"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"OR"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"UPDATE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"ON"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"emp"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"FOR"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"EACH"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"ROW"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"EXECUTE"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"PROCEDURE"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"emp_stamp"},
+  {"type":"Punctuation","value":"();"},
+  {"type":"Text","value":"\n\n"},
+  {"type":"Keyword","value":"DO"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"language"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"plpgsql"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringHeredoc","value":"$$"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"declare"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"r"},
+  {"type":"Text","value":" "},
+  {"type":"NameBuiltin","value":"record"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"begin"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"for"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"r"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"in"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"select"},
+  {"type":"Text","value":" "},
+  {"type":"Operator","value":"*"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"from"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"books"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"loop"},
+  {"type":"Text","value":"\n  "},
+  {"type":"Keyword","value":"execute"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"'select '''"},
+  {"type":"Text","value":" "},
+  {"type":"Operator","value":"||"},
+  {"type":"Text","value":" "},
+  {"type":"Name","value":"r"},
+  {"type":"LiteralNumberFloat","value":"."},
+  {"type":"Name","value":"title"},
+  {"type":"Text","value":" "},
+  {"type":"Operator","value":"||"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringSingle","value":"''''"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"end"},
+  {"type":"Text","value":" "},
+  {"type":"Keyword","value":"loop"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n"},
+  {"type":"Keyword","value":"end"},
+  {"type":"Text","value":"\n"},
+  {"type":"LiteralStringHeredoc","value":"$$"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n\n"},
+  {"type":"Keyword","value":"DO"},
+  {"type":"Text","value":" "},
+  {"type":"LiteralStringHeredoc","value":"$$\ndeclare r record;\nbegin\n  for r in select * from books\nloop\n  execute 'select ''' || r.title || '''';\nend loop;\nend\n$$"},
+  {"type":"Punctuation","value":";"},
+  {"type":"Text","value":"\n"},
+  {"type":"LiteralString","value":"```"},
+  {"type":"Error","value":"\n"}
+]
diff --git a/regexp.go b/regexp.go
index 75fb5d0..7c0586b 100644
--- a/regexp.go
+++ b/regexp.go
@@ -33,7 +33,7 @@ func (e EmitterFunc) Emit(groups []string, lexer Lexer) Iterator { return e(grou
 func ByGroups(emitters ...Emitter) Emitter {
 	return EmitterFunc(func(groups []string, lexer Lexer) Iterator {
 		iterators := make([]Iterator, 0, len(groups)-1)
-		// NOTE: If this panics, there is a mismatch with groups. Uncomment the following line to debug.
+		// NOTE: If this panics, there is a mismatch with groups
 		for i, group := range groups[1:] {
 			iterators = append(iterators, emitters[i].Emit([]string{group}, lexer))
 		}
@@ -41,6 +41,74 @@ func ByGroups(emitters ...Emitter) Emitter {
 	})
 }
 
+// UsingByGroup emits tokens for the matched groups in the regex using a
+// "sublexer". Used when lexing code blocks where the name of a sublexer is
+// contained within the block, for example on a Markdown text block or SQL
+// language block.
+//
+// The sublexer will be retrieved using sublexerGetFunc (typically
+// internal.Get), using the captured value from the matched sublexerNameGroup.
+//
+// If sublexerGetFunc returns a non-nil lexer for the captured sublexerNameGroup,
+// then tokens for the matched codeGroup will be emitted using the retrieved
+// lexer. Otherwise, if the sublexer is nil, then tokens will be emitted from
+// the passed emitter.
+//
+// Example:
+//
+//	var Markdown = internal.Register(MustNewLexer(
+//		&Config{
+//			Name:      "markdown",
+//			Aliases:   []string{"md", "mkd"},
+//			Filenames: []string{"*.md", "*.mkd", "*.markdown"},
+//			MimeTypes: []string{"text/x-markdown"},
+//		},
+//		Rules{
+//			"root": {
+//				{"^(```)(\\w+)(\\n)([\\w\\W]*?)(^```$)",
+//					UsingByGroup(
+//						internal.Get,
+//						2, 4,
+//						String, String, String, Text, String,
+//					),
+//					nil,
+//				},
+//			},
+//		},
+//	))
+//
+// See the lexers/m/markdown.go for the complete example.
+//
+// Note: panic's if the number emitters does not equal the number of matched
+// groups in the regex.
+func UsingByGroup(sublexerGetFunc func(string) Lexer, sublexerNameGroup, codeGroup int, emitters ...Emitter) Emitter {
+	return EmitterFunc(func(groups []string, lexer Lexer) Iterator {
+		// bounds check
+		if len(emitters) != len(groups)-1 {
+			panic("UsingByGroup expects number of emitters to be the same as len(groups)-1")
+		}
+
+		// grab sublexer
+		sublexer := sublexerGetFunc(groups[sublexerNameGroup])
+
+		// build iterators
+		iterators := make([]Iterator, len(groups)-1)
+		for i, group := range groups[1:] {
+			if i == codeGroup-1 && sublexer != nil {
+				var err error
+				iterators[i], err = sublexer.Tokenise(nil, groups[codeGroup])
+				if err != nil {
+					panic(err)
+				}
+			} else {
+				iterators[i] = emitters[i].Emit([]string{group}, lexer)
+			}
+		}
+
+		return Concaterator(iterators...)
+	})
+}
+
 // Using returns an Emitter that uses a given Lexer for parsing and emitting.
 func Using(lexer Lexer) Emitter {
 	return EmitterFunc(func(groups []string, _ Lexer) Iterator {