The difference is that use executes the module's code at compile time, basically making $File::Find::prune known earlier than with require, which executes at runtime. One really simple workaround is to use the variable twice: $File::Find::prune = $File::Find::prune = 1; (Update: Of course this removes typo protection if you happen to make the same typo twice, e.g. if you used copy&paste on the variable name.)