Regular expression cheatsheetEdit
Perl-compatible regular expression syntax
- Negative lookahead: 
foo(?!bar) 
- Negative lookbehind: 
(?<!foo)bar 
- Positive lookahead: 
foo(?=bar) 
- Positive lookbehind: 
(?<=foo)bar 
foo(?!bar)(?<!foo)barfoo(?=bar)(?<=foo)bar