I think what you're looking for in place of "fingerprint" is "(interface) contract" - the concept that a class "promises to behave like (f.ex) a CGI object". And indeed, groping around on CPAN and finding Class::Contract, its goals seem to be much like what you are talking about.

Makeshifts last the longest.

In reply to Re^3: Class::Interface -- isa() Considered Harmful by Aristotle
in thread Class::Interface -- isa() Considered Harmful by chromatic

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