If Perl had better support for anonymous classes a simple solution would be to just create a specialization of the Divisor class (i.e. a subclass).

# Pseudo code!

my $two = new subclass of Divisor {
  sub divides { $_[1] =~ /[02468]\z/ }
};
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There would be no need to modify or redefine anything in the Divisor class.

lodin