#!/usr/bin/perl 
use Win32::SerialPort; 

$PortObj->are_match("abcd"); # Pattern to match
my $gotit = "";
until ("" ne $gotit) {
$gotit = $PortObj->lookfor(); # Look for the pattern "abcd" in the incoming data
if($gotit){last;} # to exit the loop after the pattern detection

print("Pattern is not detected\n"); # print the message till pattern is detected.
# send some command through serial port in loop till the pattern is detectd
}

# send next command after the pattern detection.