First, please don't use string eval for something like:

eval "sub $action { my \$pkg = shift; return(\$pkg->{\"$action\"}); }"
+;
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It's far better instead to compile that code once, plugging in the parts that are variable, using a closure, like:

{
  my $action = "whatever";
  no strict 'refs';
  *{$action} = sub { my $pkg = shift; return $pkg->{$action}; };
}
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There. No nasty runtime eval, meaning no "firing up the compiler" every time you add a method (s-l-o-o-o-o-o-w), nor worries that if $action contains quote-character messiness, you'll get clobbered.

Second, the class package (where the methods are kept) is not per-object, but shared amongst all objects. So if one object added a "blah" method, that would be seen by all objects.

Maybe what you want is one of the classless object solutions, like Class::Prototyped by the Monestary's own bikeNomad. That lets you create lightweight classes with methods that are specific to that object. In fact, you can then inherit from that (very Self-like, if you're familiar with Self).

-- Randal L. Schwartz, Perl hacker