1) check the return result of system command

   system("pscp ....") or {
     open $log, ">C:\pscp.log";
     print $log "Can not execute the pscp command.";
     close $log;
     exit(1);
   }

2) add -v (verbose) option to your pscp command to print more info.
   redirect output of your pscp command to a log file.

   system("pscp .... -v >> c:\pscp.log 2>&1");