...
 my ($exe, $cmd) = ('/usr/bin/rsh', 'ps -fl r -u username');
 my $cnt = 0;

 for my $node ( sort @nodes ) {
   my @res = grep !(/$cmd/ || /STIME/), split /[\n\r]+/, qx{$exe $node $cmd};
   my $nproc = scalar @res;   # how many processes

   if( $nproc ) {
      print map
         "Do " . "some ". "formatting of " . "ps -fl output here!",
           @res
   }
  ...
  ++$cnt
  ...