When doing this, keep in mind that using backticks (``) or the qx// quote-like operator, the command provided is passed through the shell (/bin/sh, whatever THAT really is) and subject to all the usual shell magic. This may be a problem if you're not expecting it, and a security issue if you're passing user input to the shell.

In order to avoid the shell, use system instead and pass a list:

#!/usr/bin/perl

# ...

system ("mkdir", "-p", map { "$dir/$_" } @files);
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