in reply to User input while process is running.

Have a look at IPC::Run for a robust implementation of this, or for simple uses that don't require pty emulation and you don't need to capture the output, open will do what you want. Here's a barebones look at both:

use 5.010; use autodie; # With basic open() open my $sort, '|-', 'sort -n'; printf $sort "%d\n", rand 100 for 1..10; close $sort; # With IPC::Run use IPC::Run qw/start finish pump/; print "IPC::Run output:\n"; my $r = start [ 'perl' ], \my $in, \my $out, \my $err or die "Can't start: $!"; $in .= 'print "Hello, world!\n";'; finish $r; say $out; die 'ERROR: $err' if length $err;


13 14 34 37 44 63 83 86 90 95 IPC::Run output: Hello, world!
use strict; use warnings; omitted for brevity.