#!/usr/bin/env perl
use warnings; # you forgot
use strict;   # these two babies

open my $abc, '|-', '/oracle/pieces/abc.sh' or die "open: $!";
print $abc "y\n" for 1 .. 3;
close $abc or die "close: $!";

# You probably want to check to make sure abc did not fail, even if you use
# modules to start the process for you.
if ($? != 0) {
    if ($? & 127) { printf STDERR "abc died with signal %d\n", $? & 127 }
    else { printf STDERR "abc exited with error code %d\n", $? >> 8 }
    exit 1;
}