#!/usr/bin/env perl

use strict;
use warnings;
use autodie qw{:all};

use Capture::Tiny qw{capture};

my ($stdout, $stderr) = capture \&run_external_command;

printf "STDOUT: %sSTDERR: %s\n", $stdout, $stderr;

sub run_external_command {
    my $external_command = 'cat';
    open my $cmd_pipe, '|-', $external_command;
    print $cmd_pipe "password\n";
}