Document use of - in a regex char class.

Subject: [PATCH] Re: regex matcher incorrect

At 13:17 +0200 1997-06-24, Ulrich Windl wrote:
>In a statement like "$_[0] =~ /^([ugoa]+)([+-=])([rwxst]*)$/;" some
>incorrect patterns were matched. As an example "go/rw" was matched.
>Adding a backslash in front of the minus, making "[+\-=]", solved the
>problem.
>
>As this is a non-obvious feature, I'd consider that as a bug. Originally
>the problem was seen on Linux running the same version of Perl.

Thanks Ulrich.  You're right.   While all UNIX-descended regular expression
packages work pretty much the same way in respect how you make "-" a member
of a character class, neither the documentation delivered with Perl nor the
book "Programming Perl" tells you what to do, and they should.  Here's a
patch to apply to the perlre.pod documentation file:

p5p-msgid: v03102804afd578bcef2c@[194.51.248.88]

diff --git a/pod/perlre.pod b/pod/perlre.pod
index 2b24379..37434a6 100644 (file)
--- a/pod/perlre.pod
+++ b/pod/perlre.pod
@@ -515,7 +515,11 @@ in C<[]>, which will match any one of the characters in the list.  If the
 first character after the "[" is "^", the class matches any character not
 in the list.  Within a list, the "-" character is used to specify a
 range, so that C<a-z> represents all the characters between "a" and "z",
-inclusive.
+inclusive.  If you want "-" itself to be a member of a class, put it
+at the start or end of the list, or escape it with a backslash.  (The
+following all specify the same class of three characters: C<[-az]>,
+C<[az-]>, and C<[a\-z]>.  All are different from C<[a-z]>, which
+specifies a class containing twenty-six characters.)
 
 Characters may be specified using a metacharacter syntax much like that
 used in C: "\n" matches a newline, "\t" a tab, "\r" a carriage return,