package myDebugger;

use strict;
use warning;
use Win32;
use Win32::OLE;
use Win32::OLE qw( in with );
use Win32::OLE::Const 'UDE';
...

my $debugger;

sub GetInstance {
	if ( defined $debugger) {
		return $debugger;
	}
	else {
                #Initialize Debugger and set $debugger
		DebuggerInit();
		(defined $debugger) ? return $debugger
		  : print "Can't initialize debugger, please check!" );
		return 0;
	} 
}