My ex-employers own the last ones I wrote, but they're pretty simple. Use File::Find to traverse a hierarchy, then ignore file types that aren't interesting (like .doc or .exe), and finally processing files that are. Stripped of extraneous detail, they look something like:

use File::Find;

my $ignore = '(?:\.exe|\.doc)$';

find(\&consider, $root);
emit_report();

sub consider {
    my $path = $File::Find::path;

    return if $path =~ m/$ignore/o;

    process($path);
}
[download]

Sure, the basic structure is simple. The good bits are those helpful regexes that spot naughty coding. That's the hard part. Still, probably worth doing. Thanks for the tip.

-sam