Hi. I have a pm module that has been working find till now. However recently with structuring the code I now get the following message (last item of console output);

 
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:/S
+trawberry/perl/vendor/lib/Win32API/CommPort.pm line 217.
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The last bit indicates a buffer overflow, despite the fact that the serial port (Com5) has worked quite well up to that point. The Win32::SerialPort is packed in my own pm module which is presented below;

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 th
+e 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 "U
+nable 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 ( $response, -1 );    # get the last charact
+er
        if ($last eq ">") { $loop = 0; 
                             # $response = substr( $response, 0, -1); 
+    # -1 removes the ">";  #Leave the ">" character
                             # chomp $response;     # only removes lin
+efeeds 
                             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;
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On doing a subroutine call Serial_TrxRcv it crashes here where indicated (with "IT CRASHES HERE !!!!!"). This is after many uses of the subroutine. This is easily correlated with the console output (presented). What is my issue ? Do I need to clear the buffer ?

Regards JC.....