Console output
--------------
cmd; AT @2 x x
AT_@2          Cmd; AT @2 Length; 15  Response; 0123456789AB__>.

cmd; 01 00 x x

PIDs01_20      Cmd; 01 00 Length; 21  Response; 41 00 BE 1F B8 11 __>.

cmd; 01 20 x x

PIDs21_40      Cmd; 01 20 Length; 21  Response; 41 20 80 06 00 11 __>.

cmd; 01 40 x x

PIDs41_60      Cmd; 01 40 Length; 21  Response; 41 40 78 D0 00 00 __>.

TPA 
$cmd; 0101 
cmd; 0101 xWin32::API::Call: parameter 2 had a buffer overflow at C:/Strawberry/perl/vendor/lib/Win32API/CommPort.pm line 217.

##</code><code>##

Serial.pm
----------
#!usr/bin/perl

use strict;
use warnings;

use Win32::SerialPort;
my $port;

package Serial;

require Exporter;
Exporter->import('import');

#Now declare what we permit to be visible within the module.
our @EXPORT = qw( &Serial_Init &Serial_TrxRcv &Serial_Close);

use Time::HiRes qw(usleep);

# ############ subroutine Serial_Init ###################################################

sub Serial_Init {

	my $port_name = 'COM5';
	#my $config_file = 'setup.cfg';    # use this to configure from the file

	$port = new Win32::SerialPort( $port_name ) 
	                ||  die "Unable to open: $^E\n";    # $^E EXTENDED_OS_ERROR
                                             
	#$port = new Win32::SerialPort($port_name, $config_file) || die "Unable to open: $^E\n";

	$port->handshake('none');     # none dtr rts xoff
	$port->baudrate(38400);       # 19200 57600 1200 9600 115200 4800 600 2400 300 38400
	$port->parity('none');        # space none odd even mark
	#$port->parity_enable(1); 	  #      for any parity except "none"
	$port->databits(8);           # options 7 8
	$port->stopbits(1);           # options 2 1
	$port->buffers(256, 256);
	$port->read_interval(0);      #RI
	$port->read_const_time(20);   #RC
	$port->write_char_time(1);    #WM
	$port->write_const_time(100); #WC

	print "Write settings;  ";

	$port->write_settings || undef $port;
	# A report out to the console
	my $baud   = $port->baudrate;
	my $parity = $port->parity;
	my $data   = $port->databits;
	my $stop   = $port->stopbits;
	my $hshake = $port->handshake;

	print "B = $baud, D = $data, S = $stop, P = $parity, H = $hshake\n\n";
            
	# use the below to save the current configuration
	# if ( $port ) { $port->save('setup.cfg') ; print "Serial Port OK \n" };
	
}

# ############## subroutine Serial_TrxRcv ###############
sub Serial_TrxRcv {
	
	my ($cmd) = @_;
	my $response = "";
	
	print "cmd; $cmd x";
	
	$port->write($cmd."\r");          # IT CRASHES HERE !!!!!!!
	print " x\n";
	my $loop = 1;
	while( $loop ) {
		usleep(200000);         # 0.2 of a second
		my $partial_resp;
		$partial_resp = $port->input;
        # chomp $partial_resp;     # only removes linefeeds 
		$response = $response.$partial_resp;
	   
	    # print $response;
	    
		#my $responseHex = unpack ('H*', $response);
		#print $responseHex."\n";
	     
	    my $last = substr ( $response, -1 );    # get the last character
	    if ($last eq ">") { $loop = 0; 
	    	                 # $response = substr( $response, 0, -1);     # -1 removes the ">";  #Leave the ">" character
	    	                 # chomp $response;     # only removes linefeeds 
	    	                 next; 
	                      }
	    print ".";
	}
	
	return $response;	
}

# ############## subroutine Serial_Close #################
sub Serial_Close {
	$port->close();
}

# ############## Execute when module exits  ##############
END {
  undef $port; # free it before global destruction runs
}

1;