while (<>)
{
   next if /^\s*\#/;  # comment
   next if /^\s*$/;   # empty line
   do_the_work($_);
}

##</code><code>##

while (<>)
{
   if (not /^\s*\#/ and
       not /^\s*$/)
   {
      do_the_work($_);
   }
}