From perldoc perlop:

qw/STRING/

Evaluates to a list of the words extracted out of STRING, using embedd
+ed whitespace as the word delimiters.

--removed by me you can see the rest in perldoc perlop--

A common mistake is to try to separate the words with comma or to put 
+comments into a multi-line qw-string. For this reason, the use warnin
+gs pragma and the -w switch (that is, the $^W variable) produces warn
+ings if the STRING contains the ``,'' or the ``#'' character.
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As you can see placing placing comments in qw() is a common mistake ;) when in doubt always read the docs, and always use warnings; use strict;.