for my $fastarray ( @fastarray ) {
    my $hash = $matches{ $fastarray };

    for my $site ( sort { $a <=> $b } keys %$hash ) {

        for my $lowerlimit ( @{ $hash->{ $site } } ) {
            my $upperlimit = $span + $lowerlimit;

            for my $sitekey ( sort { $a <=> $b } keys %$hash ) {
                push @{ $sets{ $fastarray } }, { $sitekey => undef };
                my @arrayA = grep { $_ >= $lowerlimit && $_ <= $upperlimit } @{ $hash->{ $sitekey } }
                    or next;
                $sets{ $fastarray }[ -1 ]{ $sitekey } = \@arrayA;
                print "\$sets{$fastarray}[-1] is:\n", Dumper $sets{ $fastarray }[ -1 ];
                }
            }
        }