turn on debug below perl code

abcdef1

How to turn on debug in function sendSMTP ??
What is the fucntion var $debug ??

[code]
#!/usr/bin/perl -w

use Socket;
use strict;

my($mailTo) = 'chuikingman@yahoo.com.hk';
my($mailServer) = 'mail.hgcbroadband.com';

my($mailFrom) = 'medined@mtolive.com';
my($realName) = "chuikingman";
my($subject) = 'Test send_mail';
my($body) = "Test Line One.
Test Line Two.
";

$main::SIG{'INT'} = 'closeSocket';

my($proto) = getprotobyname("tcp") || 6;
my($port) = getservbyname("SMTP", "tcp") || 25;
my($serverAddr) = (gethostbyname($mailServer))[4];

die('gethostbyname failed.') unless (defined($serverAddr));

socket(SMTP, AF_INET(), SOCK_STREAM(), $proto)
or die("socket: $!");

my $packFormat;
$packFormat = 'S n a4 x8'; # Windows 95, SunOs 4.1+
#$packFormat = 'S n c4 x8'; # SunOs 5.4+ (Solaris 2)

connect(SMTP, pack($packFormat, AF_INET(), $port, $serverAddr))
or die("connect: $!");

select(SMTP); $| = 1; select(STDOUT); # use unbuffered i/o.

{
my($inpBuf) = '';

recv(SMTP, $inpBuf, 200, 0);
recv(SMTP, $inpBuf, 200, 0);
}
my $debug = 1 ;
sendSMTP(1, "HELO
");
sendSMTP(1, "MAIL From: <$mailFrom>
");
sendSMTP(1, "RCPT To: <$mailTo>
");
sendSMTP(1, "DATA
");

send(SMTP, "From: $realName
", 0);
send(SMTP, "Subject: $subject
", 0);
send(SMTP, $body, 0);

sendSMTP(1, "
.
");
sendSMTP(1, "QUIT
");

close(SMTP);

sub closeSocket { # close smtp socket on error
close(SMTP);
die("SMTP socket closed due to SIGINT
");
}

sub sendSMTP {
my($debug) = shift;
#my($debug) = 1;
my($buffer) = @_;

print STDERR ("> $buffer") if $debug;
send(SMTP, $buffer, 0);

recv(SMTP, $buffer, 200, 0);
print STDERR ("< $buffer") if $debug;

return( (split(/ /, $buffer))[0] );
}




[/code]