use strict;
use Time::HiRes;

sub CheckNaughtiness ()
{
   my $text = 'x' x 10_000;

   my $start = Time::HiRes::time();
   for (my $i = 0; $i < 5_000; $i++) { }
   my $overhead = Time::HiRes::time() - $start;

   $start = Time::HiRes::time();
   for (my $i = 0; $i < 5_000; $i++) { $text =~ m/^/}
   my $delta = Time::HiRes::time() - $start;

   printf "It seems your code is %s (overhead=%.2f, delta=%.2f)\n",
      ($delta > $overhead*5) ? "naughty" : "clean", $overhead, $delta;
}