#! /usr/bin/perl

# debugging levels
use constant NONE   =>  0;
use constant BUG    =>  2**0;
use constant TRACE  =>  2**1;
use constant ALL    =>  2**2 - 1;

# current level
use constant DEBUG => NONE;

sub routine {
   warn "debug message" if DEBUG && "something";
   warn "trace message" if DEBUG & TRACE;
}