my $cmd = "cp $foo $bar";
my $r = system($cmd);
if ($r) {
    if ($? == -1) {
        die "failed to execute '$cmd': $!\n";
    }
    elsif ($? & 127) {
        my $msg
          = sprintf "'$cmd' failed with signal %d, %s coredump\n",
          ($? & 127), ($? & 128) ? 'with' : 'without';
        die $msg;
    }
    else {
        die "'$cmd' exited with value %d\n", $? >> 8;
    }
}

##</code><code>##

    copy($foo, $bar) or die "cannot copy $foo to $bar: $!";