Assuming they are both sorted lists this will find if @$s is in @$a

sub in_ordered_set {
    my ($s,$a)=@_;
    return 1 unless @$s;
    return 0 unless @$a;
    my ($i,$j)=(0,0);
    while ($i<@$s) {
      while ($j<@$a) {
        last if $a->[$j]==$s->[$i];
        return 0 if $a->[$j]>$s->[$i];
        $j++;
      }
      return 0 if $j>=@$a; # Updated 
      $j++;
      $i++;
    }
    return 1
}
[download]

But generally you will want to do this lookup many times on @$a so in that case you should build a hash.

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demerphq

_{<Elian> And I do take a kind of perverse pleasure in having an OO assembly language...}

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• Update:  
Fixed bug in code: would return true trying to find 3,4 in 1,2,3.