use strict;

print pad($_,5), "\n" for (qw(3.14 1 10 100 1000));

sub pad {
   my ($str,$pad) = @_;
   my ($add,$right);

   ($str,$right) = split('\.',$str,2);
   $right = ($right) ? ".$right" : '';
   $add   = $pad - length($str);

   return $str . $right if $add < 1;
   return ('0' x $add) . $str . $right;
}

##</code><code>##

old: return $str if $add < 1;
new: return $str . $right if $add < 1;