use IO::Socket;
    use IO::Select;

    my $COMport=33;

    while (1)
    {
		#open Port or die if blocked / wrong port
        if (!open( PORT, "+>\\\\.\\COM$COMport" ))
			{  
				die ("Can't open COM$COMport");
			}
			PORT->autoflush(1);
			PORT->flush();
			print "\nEnter AT command:";
			my $ATcmd=<STDIN>;
			chomp($ATcmd); 		# remove CRLF
			$ATcmd =~ s/^\s+//;		# remove leading space
			$ATcmd =~ s/\s+$//;            # remove trailing space
			print "Sending: '$ATcmd'\n";
			print PORT $ATcmd . "\r\n";
		
			print "reading\n";
			#Reading the response
			while (my $ret=<PORT>)
			{   
				print $ret;
				if ($ret=~/^OK/ || $ret=~/^ERROR/) { last}
			}
			close(PORT);
    }

    print "done!";