my $line = 'Oct  9 08:50:53 mail_server sendmail[30172]: j99FopoN030172: from=<support@symantec.com>, size=0, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=[218.1.114.182]';

if ($line =~ /relay=\[(.*?)\]/) {
	print $1;
}