Document tests failing when threaded, since we now have more.

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

diff --git a/pod/perlobj.pod b/pod/perlobj.pod
index d1938ab..e466dc7 100644 (file)
--- a/pod/perlobj.pod
+++ b/pod/perlobj.pod
@@ -361,21 +361,41 @@ are inherited by all other classes:
 
 C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS>
 
-C<isa> is also exportable and can be called as a sub with two arguments. This
-allows the ability to check what a reference points to. Example
+You can also call C<UNIVERSAL::isa> as a subroutine with two arguments.
+The first does not need to be an object or even a reference.  This
+allows you to check what a reference points to, or whether
+something is a reference of a given type. Example
 
-    use UNIVERSAL qw(isa);
-
-    if(isa($ref, 'ARRAY')) {
+    if(UNIVERSAL::isa($ref, 'ARRAY')) {
        #...
     }
 
+To determine if a reference is a blessed object, you can write
+
+    print "It's an object\n" if UNIVERSAL::isa($val, 'UNIVERSAL');
+
 =item can(METHOD)
 
 C<can> checks to see if its object has a method called C<METHOD>,
 if it does then a reference to the sub is returned, if it does not then
 I<undef> is returned.
 
+C<UNIVERSAL::can> can also be called as a subroutine with two arguments.
+It'll always return I<undef> if its first argument isn't an object or a
+class name.    So here's another way to check if a reference is a
+blessed object
+
+    print "It's still an object\n" if UNIVERSAL::can($val, 'can');
+
+You can also use the C<blessed> function of Scalar::Util:
+
+    use Scalar::Util 'blessed';
+
+    my $blessing = blessed $suspected_object;
+
+C<blessed> returns the name of the package the argument has been
+blessed into, or C<undef>.
+
 =item VERSION( [NEED] )
 
 C<VERSION> returns the version number of the class (package).  If the
@@ -397,8 +417,7 @@ strange effects if the Perl code dynamically changes @ISA in any package.
 
 You may add other methods to the UNIVERSAL class via Perl or XS code.
 You do not need to C<use UNIVERSAL> to make these methods
-available to your program.  This is necessary only if you wish to
-have C<isa> available as a plain subroutine in the current package.
+available to your program (and you should not do so).
 
 =head2 Destructors