use strict;
use warnings;

use POSIX qw( dup2 );

open(my $src1_fh, '-|', echo => 'apples')
   or die("open: $!");
open(my $src2_fh, '-|', echo => 'oranges')
   or die("open: $!");

dup2(fileno($src1_fh), 63)
   or die("dup2: $!");
dup2(fileno($src2_fh), 64)
   or die("dup2: $!");

system(diff => '/dev/fd/63', '/dev/fd/64') >= 0
   or die("system: $!");

printf("\$?=%04X\n", $?);