Oh oh. Here's the same non-buggy version that does invoke the shell. To fix the bug in your code, you'll need to follow symlinks and whenever considering entering a directory, decide whether you've been there before. Symlinks will cause your existing code to enter infinite loops and to run the command on some things more than once.

#!perl -w
use strict;
use File::Find;

my ( $start_dir, $command ) = @ARGV;
find( sub { system $command if -d }, $start_dir );
[download]