I'm not sure what the official mechanism for making such a suggestion would be, but I recently had to go on a bug hunt in my code that left me surprised use warnings didn't give me some sort of, "are you SURE you aren't doing something silly here at line x?" message. Maybe it isn't practical to expect use warnings to save me from myself in this case, but I figured I'd throw it out here as a meditation for discussion and to get opinions from Monks far wiser than I am.

I'm of course simplifying and paraphrasing, but essentially I had some code that did the following:

open(my $first_fh, "<", "file1.txt") or die "Cannot open \"file1.txt\"
+: $!.";
open(my $second_fh, "<", "file2.txt") or die "Cannot open \"file2.txt\
+": $!.";

my @file1_lines = <$first_fh>;
close $first_fh;

while (my $line = <$second_fh>)
{
    my @data = my_sub($first_fh, $line); # copy/paste error, should ha
+ve passed $second_fh here

    # and of course a bunch of non-relevant stuff here
}
[download]

So I accidentally passed the $first_fh that I had previously closed to my_sub, but as it turns out use warnings didn't make a peep about this. I did of course get warnings from inside my_sub when it attempted to make use of the filehandle, but the kicker was that any such use was wrapped inside of a conditional that actually made it very rare it would ever get used (maybe once every 100,000 lines or so of typical data).

DISCLAIMER: The fact that I didn't have something in my standard test data that ensured the conditional that used the filehandle was exercised is entirely on me (forgive me, for I have sinned). I accept full responsibility for that mistake and the initial copy/paste laziness error that forced me to engage in my bug hunt. I'm only pointing out that usually use strict, use warnings, or perl itself is pretty good about preemptively saving me from myself, and in this case it didn't.

Any thoughts from the Monastery?