qw/STRING/ Evaluates to a list of the words extracted out of STRING, using embedded 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 warnings pragma and the -w switch (that is, the $^W variable) produces warnings if the STRING contains the ``,'' or the ``#'' character.