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Matchable is a drop-in compatible replacement for Chicken's MATCH macro. All forms are provided under the same name, and all features except the ..k pattern are supported.
In addition, matchable supports non-linear patterns, i.e. patterns where an identifier occurs multiple times, requiring all instances of the identifier to be EQUAL?. For example:
(x _ x)
matches all lists of three elements whose first and third elements are the same.
For full documentation, see Pattern matching.