Parse::Flex works similar to Parse::Lex, but it uses XS for faster
performance.

This module allows you to construct a lexer analyzer with your custom
rules. Parse::Flex is not intended to be used directly; instead, use the
script makelexer.pl to submit your grammar file. The output of the script
is a custom shared library and a custom .pm module which, among other
things, will transparently load the library and provide interface to your
(custom) lexer. In other words, you supply a grammar.l file to
makelexer.pl and you receive Flex01.pm and Flex02.so . Then, use only the
Flex01.pm - since Flex01.pm will automatically load Flex01.so.

The grammar.l file requires the same syntax as flex(1); that is, the
actions are written in C . See the flex(1) documentation to learn the
syntax, or fetch the sample t/grammar.l file inside this package.