in reply to How to determine if a package method is defined

Not quite a direct answer to the question but you can can. 

cow@moo>perl -MCGI -le 'print CGI->can("param") ? "yes" : "no"'
yes
cow@moo>perl -MCGI -le 'print CGI->can("paramz") ? "yes" : "no"'
no

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See UNIVERSAL and search around in here for more on it.

In Section Seekers of Perl Wisdom