As ysth pointed out, you need to use the non c-style for loop. In addition, you have to initialize $product to 1 each time through the loop. And if you want to make your program more Perl-like, you should always use warnings; (as well as strict) - perl would have complained about the uninitialized $product.

So, this works for me:

use strict;
use warnings;

my ($product,@values);

@values = (7,38,44,2,0);

foreach my $number (@values)
{
  unless($number == 0)
  {
    print $number;
    # $product *= $number for(1 .. $number);
    $product = 1;
    $product *= $_ for(1 .. $number);
    print " Factorial is $product\n";
   }
   else { print "0 Factorial is 1\n"; }
}
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