Supported regular expression features
The listings are taken from the Perl regex docs. Regular expressions are applied via the regex metafunction.
Currently supported or planned features
Modifiers
| Modifier |
Notes |
Status |
i |
Do case-insensitive pattern matching. For example, "A" will match "a" under /i. |
Supported |
m |
Treat the string being matched against as multiple lines. That is, change ^ and $ from matching the start of the string's first line and the end of its last line to matching the start and end of each line within the string. |
Supported |
s |
Treat the string as single line. That is, change . to match any character whatsoever, even a newline, which normally it would not match. |
Supported |
*x and xx |
Extend your pattern's legibility by permitting whitespace and comments. For details see: Perl regex docs: /x and /xx. |
Supported |
n |
Prevent the grouping metacharacters ( and ) from capturing. This modifier will stop $1, $2, etc. from being filled in. |
Supported |
c |
Keep the current position during repeated matching. |
Planned |
Escape sequences (Complete)
| Escape sequence |
Notes |
Status |
\t |
Tab (HT, TAB)X |
Supported |
\n |
Newline (LF, NL) |
Supported |
\r |
Return (CR) |
Supported |
\f |
Form feed (FF) |
Supported |
\a |
Alarm (bell) (BEL) |
Supported |
\e |
Escape (think troff) (ESC) |
Supported |
\x{}, \x00 |
Character whose ordinal is the given hexadecimal number |
Supported |
\o{}, \000 |
Character whose ordinal is the given octal number |
Supported |
Quantifiers (Complete)
| Quantifier |
Notes |
Status |
* |
Match 0 or more times |
Supported |
+ |
Match 1 or more times |
Supported |
? |
Match 1 or 0 times |
Supported |
{n} |
Match exactly n times |
Supported |
{n,} |
Match at least n times |
Supported |
{,n} |
Match at most n times |
Supported |
{n,m} |
Match at least n but not more than m times |
Supported |
|
|
|
*? |
Match 0 or more times, not greedily |
Supported |
+? |
Match 1 or more times, not greedily |
Supported |
?? |
Match 0 or 1 time, not greedily |
Supported |
{n}? |
Match exactly n times, not greedily (redundant) |
Supported |
{n,}? |
Match at least n times, not greedily |
Supported |
{,n}? |
Match at most n times, not greedily |
Supported |
{n,m}? |
Match at least n but not more than m times, not greedily |
Supported |
|
|
|
*+ |
Match 0 or more times and give nothing back |
Supported |
++ |
Match 1 or more times and give nothing back |
Supported |
?+ |
Match 0 or 1 time and give nothing back |
Supported |
{n}+ |
Match exactly n times and give nothing back (redundant) |
Supported |
{n,}+ |
Match at least n times and give nothing back |
Supported |
{,n}+ |
Match at most n times and give nothing back |
Supported |
{n,m}+ |
Match at least n but not more than m times and give nothing back |
Supported |
Character Classes and other Special Escapes (Complete)
| Feature |
Notes |
Status |
[...] |
Match a character according to the rules of the bracketed character class defined by the "...". Example: [a-z] matches "a" or "b" or "c" ... or "z" |
Supported |
[[:...:]] |
Match a character according to the rules of the POSIX character class "..." within the outer bracketed character class. Example: [[:upper:]] matches any uppercase character. |
Supported |
\g1 or \g{-1} |
Backreference to a specific or previous group. The number may be negative indicating a relative previous group and may optionally be wrapped in curly brackets for safer parsing. |
Supported |
\g{name} |
Named backreference |
Supported |
\k<name> |
Named backreference |
Supported |
\k'name' |
Named backreference |
Supported |
\k{name} |
Named backreference |
Supported |
\w |
Match a "word" character (alphanumeric plus "_", plus other connector punctuation chars plus Unicode marks) |
Supported |
\W |
Match a non-"word" character |
Supported |
\s |
Match a whitespace character |
Supported |
\S |
Match a non-whitespace character |
Supported |
\d |
Match a decimal digit character |
Supported |
\D |
Match a non-digit character |
Supported |
\v |
Vertical whitespace |
Supported |
\V |
Not vertical whitespace |
Supported |
\h |
Horizontal whitespace |
Supported |
\H |
Not horizontal whitespace |
Supported |
\1 |
Backreference to a specific capture group or buffer. '1' may actually be any positive integer. |
Supported |
\N |
Any character but \n. Not affected by /s modifier |
Supported |
\K |
Keep the stuff left of the \K, don't include it in $& |
Supported |
Assertions
| Assertion |
Notes |
Status |
\b |
Match a \w\W or \W\w boundary |
Supported |
\B |
Match except at a \w\W or \W\w boundary |
Supported |
\A |
Match only at beginning of string |
Supported |
\Z |
Match only at end of string, or before newline at the end |
Supported |
\z |
Match only at end of string |
Supported |
\G |
Match only at pos() (e.g. at the end-of-match position of prior m//g) |
Planned |
Capture groups (Complete)
| Feature |
Status |
(...) |
Supported |
| Feature |
Status |
For ^.[]$()*{}?+|\ |
Supported |
Extended Patterns
| Extended pattern |
Notes |
Status |
(?<NAME>pattern) |
Named capture group |
Supported |
(?#text) |
Comments |
Supported |
(?adlupimnsx-imnsx) |
Modification for surrounding context |
Supported |
(?^alupimnsx) |
Modification for surrounding context |
Supported |
(?:pattern) |
Clustering, does not generate a group index. |
Supported |
(?adluimnsx-imnsx:pattern) |
Clustering, does not generate a group index and modifications for the cluster. |
Supported |
(?^aluimnsx:pattern) |
Clustering, does not generate a group index and modifications for the cluster. |
Supported |
(?|pattern) |
Branch reset |
Supported |
(?'NAME'pattern) |
Named capture group |
Supported |
(?(condition)yes-pattern|no-pattern) |
Conditional patterns. |
Planned |
(?(condition)yes-pattern) |
Conditional patterns. |
Planned |
(?>pattern) |
Atomic patterns. (Disable backtrack.) |
Planned |
(*atomic:pattern) |
Atomic patterns. (Disable backtrack.) |
Planned |
Lookaround Assertions
| Lookaround assertion |
Notes |
Status |
(?=pattern) |
Positive look ahead. |
Supported |
(*pla:pattern) |
Positive look ahead. |
Supported |
(*positive_lookahead:pattern) |
Positive look ahead. |
Supported |
(?!pattern) |
Negative look ahead. |
Supported |
(*nla:pattern) |
Negative look ahead. |
Supported |
(*negative_lookahead:pattern) |
Negative look ahead. |
Supported |
(?<=pattern) |
Positive look behind. |
Planned |
(*plb:pattern) |
Positive look behind. |
Planned |
(*positive_lookbehind:pattern) |
Positive look behind. |
Planned |
(?<!pattern) |
Negative look behind. |
Planned |
(*nlb:pattern) |
Negative look behind. |
Planned |
(*negative_lookbehind:pattern) |
Negative look behind. |
Planned |
Special Backtracking Control Verbs
| Backtracking control verb |
Notes |
Status |
(*SKIP) (*SKIP:NAME) |
Start next search here. |
Planned |
(*PRUNE) (*PRUNE:NAME) |
No backtracking over this point. |
Planned |
(*MARK:NAME) (*:NAME) |
Place a named mark. |
Planned |
(*THEN) (*THEN:NAME) |
Like PRUNE. |
Planned |
(*COMMIT) (*COMMIT:arg) |
Stop searching. |
Planned |
(*FAIL) (*F) (*FAIL:arg) |
Fail the pattern/branch. |
Planned |
(*ACCEPT) (*ACCEPT:arg) |
Accept the pattern/subpattern. |
Planned |
Not planned (Mainly because of Unicode or perl specifics)
Modifiers
| Modifier |
Notes |
Status |
p |
Preserve the string matched such that ${^PREMATCH}, ${^MATCH}, and ${^POSTMATCH} are available for use after matching. |
Not planned |
a, d, l, and u |
These modifiers affect which character-set rules (Unicode, etc.) are used, as described below in "Character set modifiers". |
Not planned |
g |
globally match the pattern repeatedly in the string |
Not planned |
e |
evaluate the right-hand side as an expression |
Not planned |
ee |
evaluate the right side as a string then eval the result |
Not planned |
o |
pretend to optimize your code, but actually introduce bugs |
Not planned |
r |
perform non-destructive substitution and return the new value |
Not planned |
Escape sequences
| Escape sequence |
Notes |
Status |
\cK |
control char (example: VT) |
Not planned |
\N{name} |
named Unicode character or character sequence |
Not planned |
\N{U+263D} |
Unicode character (example: FIRST QUARTER MOON) |
Not planned |
\l |
lowercase next char (think vi) |
Not planned |
\u |
uppercase next char (think vi) |
Not planned |
\L |
lowercase until \E (think vi) |
Not planned |
\U |
uppercase until \E (think vi) |
Not planned |
\Q |
quote (disable) pattern metacharacters until \E |
Not planned |
\E |
end either case modification or quoted section, think vi |
Not planned |
Character Classes and other Special Escapes
| Character class or escape |
Notes |
Status |
(?[...]) |
Extended bracketed character class |
Not planned |
\pP |
Match P, named property. Use \p{Prop} for longer names |
Not planned |
\PP |
Match non-P |
Not planned |
\X |
Match Unicode "eXtended grapheme cluster" |
Not planned |
\R |
Linebreak |
Not planned |
Assertions
| Assertion |
Notes |
Status |
\b{} |
Match at Unicode boundary of specified type |
Not planned |
\B{} |
Match where corresponding \b{} doesn't match |
Not planned |
Extended Patterns
| Extended pattern |
Notes |
Status |
(?{ code }) |
Perl code execution. |
Not planned |
(*{ code }) |
Perl code execution. |
Not planned |
(??{ code }) |
Perl code execution. |
Not planned |
(?PARNO) (?-PARNO) (?+PARNO) (?R) (?0) |
Recursive subpattern. |
Not planned |
(?&NAME) |
Recursive subpattern. |
Not planned |
Script runs
| Script runs |
Notes |
Status |
(*script_run:pattern) |
All chars in pattern need to be of the same script. |
Not planned |
(*sr:pattern) |
All chars in pattern need to be of the same script. |
Not planned |
(*atomic_script_run:pattern) |
Without backtracking. |
Not planned |
(*asr:pattern) |
Without backtracking. |
Not planned |