package MyUtil;
use strict;
use warnings;
our $DEBUG = 0; # this is the default debug level if you don't set $YourPackage::DEBUG

sub debug {
    my ( $level, $caller, $time, $debug, @message, );
    return $DEBUG unless @_;
    $caller = (ref $_[0]) ? ref shift : ($_[0] eq __PACKAGE__) ? shift : (caller)[0];
    $debug  = exists $::{$caller}{DEBUG} ? ${$::{$caller}{DEBUG}} : $DEBUG || 0;

    if ( $_[0] =~ /^\d+$/ ) {
        $level = shift;
    }
    else {
        $level = 1;
    }

    return undef if $debug < $level;
    @message =  @_;
    return undef unless @message;
    $time = localtime; # I like the long time format because my STDERR is usually a logfile. If you change this, change the spacing on the second printf, too.

    printf STDERR "DEBUG (%s)(%3i)(%s): %s\n", $caller, $level, $time, shift @message;
    while ( my $line = shift @message ) {
        printf STDERR "DEBUG".( ' ' x (34+length $caller) ).": %s\n", $line;
    }
    return 1;
}

# and then somewhere else
package main;
our $DEBUG = 50;
use MyUtil 'debug';
debug( 49, "Hello World! it's me, process $$", "And me, another line." );
debug( 51, "Change the debug level for this one to print" );

__END__

DEBUG (main)( 49)(Sun Nov 14 14:28:34 2004): Hello World! its me, process 24665
DEBUG                                      : And me, another line