Parle pattern matching

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- Parle pattern matching

# Parle pattern matching

## Table of Contents

- Character representations
- Character classes
- Unicode character classes
- Alternation and repetition
- Anchors
- Grouping

Parle supports regex matching similar to flex. Also supported are the following POSIX character sets: `[:alnum:]`, `[:alpha:]`, `[:blank:]`, `[:cntrl:]`, `[:digit:]`, `[:graph:]`, `[:lower:]`, `[:print:]`, `[:punct:]`, `[:space:]`, `[:upper:]` and `[:xdigit:]`.

The Unicode character classes are currently not enabled by default, pass --enable-parle-utf32 to make them available. A particular encoding can be mapped with a correctly constructed regex. For example, to match the EURO symbol encoded in UTF-8, the regular expression `[\xe2][\x82][\xac]` can be used. The pattern for an UTF-8 encoded string could be `[ -\x7f]{+}[\x80-\xbf]{+}[\xc2-\xdf]{+}[\xe0-\xef]{+}[\xf0-\xff]+`.