romandas has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to analyze someone else's code and understand what it does. One small block in particular is confusing me:
if($data !~ /^[\ -\~\007\012\015\035\036\037]*$/) { $data =~ tr/[\ -\~\007\012\015\035\036\037]/ /cs; }

For purposes of testing, $data is set to a "string" of the entire ASCII table (0-255) appended together.

I expect that if the first regex (in the if) finds any character that is not in the regex, the expression evaluates to true and it enters the block. If $data consists entirely of those special characters, the expression will evaluate false.

Once in the block, the tr///cs is where my confusion lies. In the Camel book, it says that /c causes the SEARCHLIST character set to be complemented. I expect this to mean that the SEARCHLIST will now match any character that is NOT included in the list. However, the output of $data is:

&#8596;&#9650;&#9660; !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO +PQRSTUVWXYZ[\]^_`abcdefghijk lmnopqrstuvwxyz{|}~
This is considerably more than what I expect to see. Can anyone explain this bit of code to me?