Perl is dynamic enough to support this. See http://search.cpan.org/~ether/Moose-2.1403/lib/Moose/Manual/Types.pod http://search.cpan.org/~ether/Moose-2.1403/li

Perl is dynamic enough to support this. See http://search.cpan.org/~ether/Moose-2.1403/lib/Moose/Manual/Types.pod http://search.cpan.org/~ether/Moose-2.1403/lib/Moose/Manual/... and http://search.cpan.org/~ether/Moose-2.1403/lib/Moose/Manual.pod http://search.cpan.org/~ether/Moose-2.1403/lib/Moose/Manual.... Competing type systems, competing Object systems, and enough internal run-time rewriting to do whatever it is you want. See also http://search.cpan.org/~smueller/Filter-Simple-0.91/lib/Filter/Simple.pm http://search.cpan.org/~smueller/Filter-Simple-0.91/lib/Filt... for a simple rewriting filter, and the Acme namespace for all kinds of fancy experiments.