new warning "Useless use of sort in scalar context"

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

diff --git a/pod/perlunicode.pod b/pod/perlunicode.pod
index e374854..64116bc 100644 (file)
--- a/pod/perlunicode.pod
+++ b/pod/perlunicode.pod
@@ -20,7 +20,7 @@ Other encodings can be converted to perl's encoding on input, or from
 perl's encoding on output by use of the ":encoding(...)" layer.
 See L<open>.
 
-To mark the Perl source itself as being in an particular encoding,
+To mark the Perl source itself as being in a particular encoding,
 see L<encoding>.
 
 =item Regular Expressions
@@ -275,6 +275,8 @@ have their directionality defined:
     BidiWS      Whitespace
     BidiON      Other Neutrals
 
+=back
+
 =head2 Scripts
 
 The scripts available for C<\p{In...}> and C<\P{In...}>, for example
@@ -481,6 +483,8 @@ below list that have the C<Block> appended).
    Yi Radicals
    Yi Syllables
 
+=over 4
+
 =item *
 
 The special pattern C<\X> match matches any extended Unicode sequence
@@ -563,7 +567,7 @@ than one Unicode character
 
 =back
 
-What doesn't yet work are the followng cases:
+What doesn't yet work are the following cases:
 
 =over 8
 
@@ -622,20 +626,29 @@ Level 1 - Basic Unicode Support
         2.2 Categories                          - done          [3][4]
         2.3 Subtraction                         - MISSING       [5][6]
         2.4 Simple Word Boundaries              - done          [7]
-        2.5 Simple Loose Matches                - MISSING       [8]
+        2.5 Simple Loose Matches                - done          [8]
         2.6 End of Line                         - MISSING       [9][10]
 
         [ 1] \x{...}
         [ 2] \N{...}
         [ 3] . \p{Is...} \P{Is...}
-        [ 4] now scripts (see UTR#24 Script Names) in  addition to blocks
+        [ 4] now scripts (see UTR#24 Script Names) in addition to blocks
         [ 5] have negation
-        [ 6] can use look-ahead to emulate subtracion
+        [ 6] can use look-ahead to emulate subtraction (*)
         [ 7] include Letters in word characters
-        [ 8] see UTR#21 Case Mappings
+        [ 8] see UTR#21 Case Mappings: Perl implements 1:1 mappings
         [ 9] see UTR#13 Unicode Newline Guidelines
         [10] should do ^ and $ also on \x{2028} and \x{2029}
 
+(*) Instead of [\u0370-\u03FF-[{UNASSIGNED}]] as suggested by the TR
+18 you can use negated lookahead: to match currently assigned modern
+Greek characters use for example
+
+               /(?!\p{Cn})[\x{0370}-\x{03ff}]/
+
+In other words: the matched character must not be a non-assigned
+character, but it must be in the block of modern Greek characters.
+
 =item *
 
 Level 2 - Extended Unicode Support
@@ -742,6 +755,18 @@ is not extensible beyond 0xFFFF, because it does not use surrogates.
 A seven-bit safe (non-eight-bit) encoding, useful if the
 transport/storage is not eight-bit safe.  Defined by RFC 2152.
 
+=head2 Security Implications of Malformed UTF-8
+
+Unfortunately, the specification of UTF-8 leaves some room for
+interpretation of how many bytes of encoded output one should generate
+from one input Unicode character.  Strictly speaking, one is supposed
+to always generate the shortest possible sequence of UTF-8 bytes,
+because otherwise there is potential for input buffer overflow at the
+receiving end of a UTF-8 connection.  Perl always generates the shortest
+length UTF-8, and with warnings on (C<-w> or C<use warnings;>) Perl will
+warn about non-shortest length UTF-8 (and other malformations, too,
+such as the surrogates, which are not real character code points.)
+
 =head2 Unicode in Perl on EBCDIC
 
 The way Unicode is handled on EBCDIC platforms is still rather
@@ -757,7 +782,7 @@ for more discussion of the issues.
 
 =head1 SEE ALSO
 
-L<encoding>, L<Encode>, L<open>, L<bytes>, L<utf8>, L<perlretut>,
-L<perlvar/"${^WIDE_SYSTEM_CALLS}">
+L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>,
+L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}">
 
 =cut