Add perlcheat to the toc and perl.pod; regen toc.

[p5sagit/p5-mst-13.2.git] / pod / perlunicode.pod

diff --git a/pod/perlunicode.pod b/pod/perlunicode.pod
index 410204a..230c105 100644 (file)
--- a/pod/perlunicode.pod
+++ b/pod/perlunicode.pod
@@ -780,13 +780,13 @@ Level 1 - Basic Unicode Support
              capital letters with certain modifiers: the Full case-folding
              decomposes the letter, while the Simple case-folding would map
              it to a single character.
-        [ 9] see UTR#13 Unicode Newline Guidelines
+        [ 9] see UTR #13 Unicode Newline Guidelines
         [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029}
              (should also affect <>, $., and script line numbers)
              (the \x{85}, \x{2028} and \x{2029} do match \s)
 
 [a] You can mimic class subtraction using lookahead.
-For example, what TR18 might write as
+For example, what UTR #18 might write as
 
     [{Greek}-[{UNASSIGNED}]]
 
@@ -801,6 +801,9 @@ But in this particular example, you probably really want
 
 which will match assigned characters known to be part of the Greek script.
 
+Also see the Unicode::Regex::Set module, it does implement the full
+UTR #18 grouping, intersection, union, and removal (subtraction) syntax.
+
 [b] See L</"User-Defined Character Properties">.
 
 =item *
@@ -1056,6 +1059,66 @@ straddling of the proverbial fence causes problems.
 
 =back
 
+=head2 When Unicode Does Not Happen
+
+While Perl does have extensive ways to input and output in Unicode,
+and few other 'entry points' like the @ARGV which can be interpreted
+as Unicode (UTF-8), there still are many places where Unicode (in some
+encoding or another) could be given as arguments or received as
+results, or both, but it is not.
+
+The following are such interfaces.  For all of these Perl currently
+(as of 5.8.1) simply assumes byte strings both as arguments and results.
+
+One reason why Perl does not attempt to resolve the role of Unicode in
+this cases is that the answers are highly dependent on the operating
+system and the file system(s).  For example, whether filenames can be
+in Unicode, and in exactly what kind of encoding, is not exactly a
+portable concept.  Similarly for the qx and system: how well will the
+'command line interface' (and which of them?) handle Unicode?
+
+=over 4
+
+=item *
+
+chmod, chmod, chown, chroot, exec, link, mkdir
+rename, rmdir stat, symlink, truncate, unlink, utime
+
+=item *
+
+%ENV
+
+=item *
+
+glob (aka the <*>)
+
+=item *
+
+open, opendir, sysopen
+
+=item *
+
+qx (aka the backtick operator), system
+
+=item *
+
+readdir, readlink
+
+=back
+
+=head2 Forcing Unicode in Perl (Or Unforcing Unicode in Perl)
+
+Sometimes (see L</"When Unicode Does Not Happen">) there are
+situations where you simply need to force Perl to believe that a byte
+string is UTF-8, or vice versa.  The low-level calls
+utf8::upgrade($bytestring) and utf8::downgrade($utf8string) are
+the answers.
+
+Do not use them without careful thought, though: Perl may easily get
+very confused, angry, or even crash, if you suddenly change the 'nature'
+of scalar like that.  Especially careful you have to be if you use the
+utf8::upgrade(): any random byte string is not valid UTF-8.
+
 =head2 Using Unicode in XS
 
 If you want to handle Perl Unicode in XS extensions, you may find the