sub intersectPlus {
    my( $a, $b, $c, $d ) = @_;
    my %a; undef @a{ @$a };
    my %b; undef @b{ @$b };
    push @{ exists $a{ $_ } ? $d : $c }, $_ for keys %b;
    push @$d, @$c;
    return;
}

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In reply to Re: As Efficient as Possible by BrowserUk
in thread As Efficient as Possible by mr_p

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