huh? I've presented two ways of getting a child's output already! (qx// and open '-|')

Update: Here's a third way:

use IPC::Open2 qw( open2 );

sub line_count {
   my ($fname) = @_;
   my $pid = open2(my $fr_child, undef, 'cat', $fname) or die;
   1 while <$fr_child>;
   waitpid $pid, 0;
   return $.;
}
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