The class's object method can call an instance's _codemethod:

package Foo;

sub makemethod {
    my $obj = shift;
    $obj->{'_codemethod'} = shift; # takes a real code reference
                                   # in this implementation,
                                   # not a string, so renamed
}

sub callmethod {
    my $obj = shift;
    $obj->{'_codemethod'}(@_);
}

# . . .
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Don't need no stinkin' Ruby ;-)