pattern-matching language based on OMeta and Python

 Parsley is a parsing library for people who find parsers scary or annoying.
 It uses the PEG algorithm, so each expression in the grammar rules works like
 a Python expression. In particular, alternatives are evaluated in
 order, unlike table-driven parsers such as yacc, bison or PLY.
 .
 Parsley is an implementation of OMeta, an object-oriented
 pattern-matching language developed by Alessandro Warth
 <http://tinlizzie.org/ometa/>.