use IPC:;Open2;

  my ($childin,$childout,$childerr);
  my $cmd = qq(/usr/bin/ssh -i $KEYFILE $USER\@$SERVER 2>/dev/null);

  my $pid = open2 ($childout,$childin,$cmd);
  my $status = $!;
  
  # check for success here
  
  # send commands
  print $childin $line1
  print $childin $line2
  print $childin $line3
  
  etc...