It seems uncertain that a solution in Perl would necessarily assist homework in random-other-language. But if it really were Perl, the first thing that would pop into my mind would be grep, e.g.: 
my @matching = grep property( $_ ), @sg;

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-M

Free your mind

In reply to Re: Equivalence classes from equivalence relation and fingerprints by Moron
in thread Equivalence classes from equivalence relation and fingerprints by ambrus

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