Sorry if I've got the wrong end of the stick, but I take it you already can come up with the 2 arrays full of the divisors, and you then want to find from those 2 arrays the highest number that is in both arrays? If that's what you want, I think this approach might fit the bill: 
# insert these 3 lines if arrays aren't sequential
sub numerical {$a <=> $b}
@array_1 = sort numerical @array_1;
@array_2 = sort numerical @array_2;

my $array_1 = pop @array_1;
my $array_2 = pop @array_2;
while (@array_1) {
    if ($array_1 > $array_2) {
        $array_1 = pop @array_1;
    }
    elsif ($array_2 > $array_1) {
        $array_2 = pop @array_2;
    }
    else {
        print "highest common divisor = $array_2\n";
        last;
    }
}

[download]
.. i.e., just keep popping off the highest number in each array until the current pair match, and Bob's yer uncle.

§ George Sherston

In reply to Re: Finding the greatest common divisor by George_Sherston
in thread Finding the greatest common divisor by gornox_zx

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