This Perl module implements the Ook programming language as described in http://bluesorcerer.net/esoteric/ook.html At least Perl 5.6.0 is required for various reasons: one reason is a bug in Perl 5.00503 (and assumedly earlier) that makes the hello.t test to moan like this: t/hello.............untie attempted while 1 inner references still exist at t/hello.t line 7, chunk 26. The test is fine, Perl 5.00503 is not.