There is no way to find the max of N numbers without using comparison operators. However, you can just add a short function to your code for finding max:

use strict;
use warnings;

my @arr = (2,7,12,5,17,9);
print max(@arr);

sub max {
    my $max = $_[0];
    do { $max = $_[$_] if $max < $_[$_]; } for 1..$#_;
    $max;
}
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This takes linear time. Or you can use a sort, which takes O(n lg n) time:

my $max = (sort { $b <=> $a } @arr)[0];
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