Provide infrastructure for PERL_ASYNC_CHECK() style safe signals.

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

diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index 06d3b1d..82086e3 100644 (file)
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -923,7 +923,10 @@ element to return happens to be C<undef>.
 
 You may also use C<defined(&func)> to check whether subroutine C<&func>
 has ever been defined.  The return value is unaffected by any forward
-declarations of C<&foo>.
+declarations of C<&foo>.  Note that a subroutine which is not defined
+may still be callable: its package may have an C<AUTOLOAD> method that
+makes it spring into existence the first time that it is called -- see
+L<perlsub>.
 
 Use of C<defined> on aggregates (hashes and arrays) is deprecated.  It
 used to report whether memory for that aggregate has ever been
@@ -1479,7 +1482,10 @@ it exists, but the reverse doesn't necessarily hold true.
 Given an expression that specifies the name of a subroutine,
 returns true if the specified subroutine has ever been declared, even
 if it is undefined.  Mentioning a subroutine name for exists or defined
-does not count as declaring it.
+does not count as declaring it.  Note that a subroutine which does not
+exist may still be callable: its package may have an C<AUTOLOAD>
+method that makes it spring into existence the first time that it is
+called -- see L<perlsub>.
 
     print "Exists\n"   if exists &subroutine;
     print "Defined\n"  if defined &subroutine;
@@ -2876,7 +2882,7 @@ another way to protect your filenames from interpretation.  For example:
     sysopen(HANDLE, $path, O_RDWR|O_CREAT|O_EXCL)
        or die "sysopen $path: $!";
     $oldfh = select(HANDLE); $| = 1; select($oldfh);
-    print HANDLE "stuff $$\n");
+    print HANDLE "stuff $$\n";
     seek(HANDLE, 0, 0);
     print "File contains: ", <HANDLE>;
 
@@ -3500,12 +3506,13 @@ with the wrong number of RANDBITS.)
 =item read FILEHANDLE,SCALAR,LENGTH
 
 Attempts to read LENGTH bytes of data into variable SCALAR from the
-specified FILEHANDLE.  Returns the number of bytes actually read,
-C<0> at end of file, or undef if there was an error.  SCALAR will be grown
-or shrunk to the length actually read.  An OFFSET may be specified to
-place the read data at some other place than the beginning of the
-string.  This call is actually implemented in terms of stdio's fread(3)
-call.  To get a true read(2) system call, see C<sysread>.
+specified FILEHANDLE.  Returns the number of bytes actually read, C<0>
+at end of file, or undef if there was an error.  SCALAR will be grown
+or shrunk to the length actually read.  If SCALAR needs growing, the
+new bytes will be zero bytes.  An OFFSET may be specified to place
+the read data into some other place in SCALAR than the beginning.
+The call is actually implemented in terms of stdio's fread(3) call.
+To get a true read(2) system call, see C<sysread>.
 
 =item readdir DIRHANDLE