my $debug = 11;
...
print STDERR "something worked: $wombat\n" if $debug > 5;
...
print STDERR "in here: too much detail", join ", ", @_, "\n" 
   if $debug > 20;

##</code><code>##

debugprint("now entering mysub ...\n", 11);
sub debugprint($$)
{
  my ($err_str, $debug_value) = @_;
  print $err_str if $debug_value >= $debug;