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.

WWW: http://search.cpan.org/dist/Parse-Flex/