The problem is that while does not iterate over a list, it simply checks for a true value. For example, while (1){} will run forever, whereas for (1){} will run once.

The same behaviour occurs when test being evaluated is param(). Additionally, while (param()){} will not modify $_. Perhaps you tested the script without any arguments, in which case it would have behaved as expected.

Here is a simple test:

#!/usr/bin/perl
use strict;
use warnings;

use CGI qw(param);
my $runs =0;
my @num;

print "Content-type: text/plain\n\n";

while(param()) {
    printf "run %d\n", $runs++;
    if ($runs > 10) {
        print "Ran over 10 times\n";
        exit;
    }
}
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You can verify it by adding the parameters on the commandline, e.g.

perl foo.pl a=b
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