use warnings;
use strict;
use IPC::Run3 'run3';

my $in = "Foo\nBar\n";
my $out = "";
# This uses temp files:
#run3 ['/bin/cat'], \$in, \$out or die "run3";

open my $infh, '<', \$in or die $!;
open my $outfh, '>', \$out or die $!;
run3 ['/bin/cat'], $infh, $outfh or die "run3";
$?==0 or die "$?";