Regex Syntax

The library supports most of the PCRE syntax with a few exceptions:

• atomic groups
• boundaries other than ^$
• callouts
• character properties
• comments
• conditional patterns
• control characters (\cX)
• horizontal / vertical character classes (\h\H\v\V)
• match point reset (\K)
• named characters
• octal numbers
• options / modes
• subroutines
• unicode grapheme cluster (\X)

TODO more detailed regex information