sub WMSCANNERDATA
{ 
        print "Scanner Has data waiting\n";
        my ($object, $wParam, $lParam, $type, $msgcode) = @_; 
        return unless $type == 0; 
        return unless $msgcode == WM_SCANNERDATA; 

        print "Data size: $wParam\n";
        
        my $buffer= 0 x $wParam;

        # added this line to make function call work
        my $buffersize= \$wParam;
        
        my $ret=$ScanGetData->Call($ScannerHandle, $buffer, $buffersize);    # Inform scanApi.dll this application does nor handle call backs
        print "Return code: $ret";

        if ($ret != SR_SUCCESS)
        {
          &DisplayScanError($ret);
          exit;
        }
        print $buffer."\n\n";
        
        return 1; 

}