It's pretty easy to convince them. Just insist that instead of writing fragile code that blithely ignores error returns, they check and report them properly.

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;
    }
}
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This is based on the example code in perlfunc(1). Faced with writing all that just to get a correct error message on failure, any developer would prefer to encapsulate the code in some routine, called... oh, I don't know, perhaps copy()? Now while File::Copy's interface is not as crufty as system()'s, you still have to check for errors explicitly:

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

But that's a big improvement for any programmer who wants to be lazy but still write correct code. Others have mentioned the need to use multi-argument system(), otherwise your code will have (perhaps exploitable) bugs when passed filenames containing spaces or shell characters.

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