I've got perl 5.8.7 on Windows (ActiveState) - and I get no output. I'm wondering whether there is some OS-specific issue where your numbers (or some of them) are being converted to floats silently.

I'm also wondering whether it would help to try something like this:

use strict;
use warnings;

my $number_one=1;
foreach my $int ( 1 .. 600 ) {
    my $number = $int / $int;
    next if $number == $number_one;
    warn "$int / $int != 1 (== $number)\n";
}
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I'm thinking that by comparing variables to another variable, instead of a literal constant, you may get everyone to be in the same form, and thus avoid this problem.