hi there. I've been trying to work this out for a few days now. Im trying to script an ftp client to backup files from a server. using a program called ftprush. this allows the user to script commands via the windows api sendmessage. I want to be able to call this via perl and send some files as a backup server. the website provides a dll and a .exe file for doing this. but reading though the file I'm sure it can be intergrated. here is the code I've attempted. 
use Win32::GUI;
use Win32::API;
my $rushhandle = Win32::GUI::FindWindow("tfmrush", "");
$command="RushApp.Util.Standalone.Login('backup','','')";
my $copy_data_struct = pack( 'L2P', 2, length( $command ), $command );
#Win32::GUI::PostMessage($rushhandle,WM_COPYDATA,$wparm,$lpCopydatastr
+uct);
#my $SendMessage=new Win32::API("User32","SendMessage",[qw(N N N N)],'
+N');
#my $lresult=$SendMessage->Call($rushhandle,WM_COPYDATA,$wparm,$lpCopy
+datastruct);
Win32::GUI::SendMessage($rushhandle, WM_COPYDATA, 0, $copy_data_struct
+);

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here is the C code from the dll. 
  TargetWindow := FindWindow('TfmRush', nil);
  CopyDataStruct.dwData := 1000;
  CopyDataStruct.cbData := strlen(Data) + 1;
  CopyDataStruct.lpData := Data;
  wCallbackWindow.fIrcHandle := mWnd;
  SendMessage(TargetWindow, WM_COPYDATA, 0, LParam(@CopyDataStruct));

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I've left the # from my code so you can see what I've tried. I've got a feeling the error is in the pack command. but reading thou the perldoc to be honest it all goes over my head. thanks for takeing the time to read and for any help offered. Ken. **UPDATE** Thank you igelkott for all the help. I got it working :) thanks for a friend on mirc for helping too :) ykwya. 
use Win32::GUI;
use Win32::API;
use constant WM_COPYDATA => 74;
my $rushhandle = Win32::GUI::FindWindow("tfmrush", "");
my $command = "RushApp.FTP.Login('backup','',0);";
my $copy_data_struct = pack('L2P', 1000, length( $command ), $command)
+;
print Win32::GUI::SendMessage($rushhandle, WM_COPYDATA, 0, $copy_data_
+struct);

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In reply to win32::sendmessage and pack help. by Fuas

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