Your Python approach does not work in Perl, because Perl does not have "bound" subroutines like Python has.

You can, I presume, gain a very, very slim advantage by prefetching the subroutine method via $obj->can(), and then call that subroutine method with $self as its first parameter. But you'll need to benchmark that for your specific situation.

my $isInst = $self->can('isInst');
for my $var (@something) {
    $isInst->($self,$var);
};
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I believe that at least while you don't rearrange or change the class hierarchy (that is, write-access to any @ISA), Perl will cache these methods anyway, at least in later versions than Perl 5.8.8, which is two major versions behind the current supported version. In that situation, this idea will likely be slower than direct method calls in Perl.