open IN, '<', $file or die "Cannot open $file for input: $!\n";

open OUT, '>>', $file or die "Cannot open $file for append: $!\n";

open P, '|', $cmd or die "Cannot open input pipe from $cmd: $!\n";

##</code><code>##

my $whence = '<';
open my $fh, $whence, $file or die "$whence $!:$file";