perlthrtut update, by Jerry D. Hedden.

p4raw-id: //depot/perl@28738

1 files changed, 316 insertions, 277 deletions

diff --git a/pod/perlthrtut.pod b/pod/perlthrtut.pod
index 8e5b2a854f..a3e3312907 100644
--- a/pod/perlthrtut.pod
+++ b/pod/perlthrtut.pod
@@ -1,19 +1,20 @@
 =head1 NAME
 
-perlthrtut - tutorial on threads in Perl
+perlthrtut - Tutorial on threads in Perl
 
 =head1 DESCRIPTION
 
-B<NOTE>: this tutorial describes the new Perl threading flavour
-introduced in Perl 5.6.0 called interpreter threads, or B<ithreads>
-for short.  In this model each thread runs in its own Perl interpreter,
-and any data sharing between threads must be explicit.
+This tutorial describes the use of Perl interpreter threads (sometimes
+referred to as I<ithreads>) that was first introduced in Perl 5.6.0.  In this
+model, each thread runs in its own Perl interpreter, and any data sharing
+between threads must be explicit.  The user-level interface for I<ithreads>
+uses the L<threads> class.
 
-There is another older Perl threading flavour called the 5.005 model,
-unsurprisingly for 5.005 versions of Perl.  The old model is known to
-have problems, is deprecated, and support for it will be removed in release
-5.10. You are strongly encouraged to migrate any existing 5.005
-threads code to the new model as soon as possible.
+B<NOTE>: There is another older Perl threading flavor called the 5.005 model
+that used the L<Threads> class.  This old model is known to have problems, is
+deprecated, and support for it will be removed in release 5.10.  You are
+strongly encouraged to migrate any existing 5.005 threads code to the new
+model as soon as possible.
 
 You can see which (or neither) threading flavour you have by
 running C<perl -V> and looking at the C<Platform> section.
@@ -22,15 +23,9 @@ have C<use5005threads=define> you have 5.005 threads.
 If you have neither, you don't have any thread support built in.
 If you have both, you are in trouble.
 
-The user-level interface to the 5.005 threads was via the L<Threads>
-class, while ithreads uses the L<threads> class. Note the change in case.
-
-=head1 Status
-
-The ithreads code has been available since Perl 5.6.0, and is considered
-stable. The user-level interface to ithreads (the L<threads> classes)
-appeared in the 5.8.0 release, and as of this time is considered stable
-although it should be treated with caution as with all new features.
+The L<threads> and L<threads::shared> modules are included in the core Perl
+distribution.  Additionally, they are maintained as a separate modules on
+CPAN, so you can check there for any updates.
 
 =head1 What Is A Thread Anyway?
 
@@ -47,13 +42,13 @@ to show you how, when, and why.
 
 There are three basic ways that you can structure a threaded
 program.  Which model you choose depends on what you need your program
-to do.  For many non-trivial threaded programs you'll need to choose
+to do.  For many non-trivial threaded programs, you'll need to choose
 different models for different pieces of your program.
 
 =head2 Boss/Worker
 
-The boss/worker model usually has one "boss" thread and one or more
-"worker" threads.  The boss thread gathers or generates tasks that need
+The boss/worker model usually has one I<boss> thread and one or more
+I<worker> threads.  The boss thread gathers or generates tasks that need
 to be done, then parcels those tasks out to the appropriate worker
 thread.
 
@@ -106,32 +101,32 @@ presented later on.)
 
 If you have experience with other thread implementations, you might
 find that things aren't quite what you expect.  It's very important to
-remember when dealing with Perl threads that Perl Threads Are Not X
-Threads, for all values of X.  They aren't POSIX threads, or
+remember when dealing with Perl threads that I<Perl Threads Are Not X
+Threads> for all values of X.  They aren't POSIX threads, or
 DecThreads, or Java's Green threads, or Win32 threads.  There are
 similarities, and the broad concepts are the same, but if you start
 looking for implementation details you're going to be either
 disappointed or confused.  Possibly both.
 
 This is not to say that Perl threads are completely different from
-everything that's ever come before--they're not.  Perl's threading
+everything that's ever come before -- they're not.  Perl's threading
 model owes a lot to other thread models, especially POSIX.  Just as
 Perl is not C, though, Perl threads are not POSIX threads.  So if you
 find yourself looking for mutexes, or thread priorities, it's time to
 step back a bit and think about what you want to do and how Perl can
 do it.
 
-However it is important to remember that Perl threads cannot magically
+However, it is important to remember that Perl threads cannot magically
 do things unless your operating systems threads allows it. So if your
-system blocks the entire process on sleep(), Perl usually will as well.
+system blocks the entire process on C<sleep()>, Perl usually will, as well.
 
-Perl Threads Are Different.
+B<Perl Threads Are Different.>
 
 =head1 Thread-Safe Modules
 
 The addition of threads has changed Perl's internals
 substantially. There are implications for people who write
-modules with XS code or external libraries. However, since perl data is
+modules with XS code or external libraries. However, since Perl data is
 not shared among threads by default, Perl modules stand a high chance of
 being thread-safe or can be made thread-safe easily.  Modules that are not
 tagged as thread-safe should be tested or code reviewed before being used
@@ -140,7 +135,7 @@ in production code.
 Not all modules that you might use are thread-safe, and you should
 always assume a module is unsafe unless the documentation says
 otherwise.  This includes modules that are distributed as part of the
-core.  Threads are a new feature, and even some of the standard
+core.  Threads are a relatively new feature, and even some of the standard
 modules aren't thread-safe.
 
 Even if a module is thread-safe, it doesn't mean that the module is optimized
@@ -158,15 +153,15 @@ See also L</"Thread-Safety of System Libraries">.
 
 =head1 Thread Basics
 
-The core L<threads> module provides the basic functions you need to write
-threaded programs.  In the following sections we'll cover the basics,
+The L<threads> module provides the basic functions you need to write
+threaded programs.  In the following sections, we'll cover the basics,
 showing you what you need to do to create a threaded program.   After
 that, we'll go over some of the features of the L<threads> module that
 make threaded programming easier.
 
 =head2 Basic Thread Support
 
-Thread support is a Perl compile-time option - it's something that's
+Thread support is a Perl compile-time option -- it's something that's
 turned on or off when Perl is built at your site, rather than when
 your programs are compiled. If your Perl wasn't compiled with thread
 support enabled, then any attempt to use threads will fail.
@@ -175,7 +170,8 @@ Your programs can use the Config module to check whether threads are
 enabled. If your program can't run without them, you can say something
 like:
 
-    $Config{useithreads} or die "Recompile Perl with threads to run this program.";
+    use Config;
+    $Config{useithreads} or die('Recompile Perl with threads to run this program.');
 
 A possibly-threaded program using a possibly-threaded module might
 have code like this:
@@ -187,123 +183,127 @@ have code like this:
         if ($Config{useithreads}) {
             # We have threads
             require MyMod_threaded;
-           import MyMod_threaded;
+            import MyMod_threaded;
         } else {
-           require MyMod_unthreaded;
-           import MyMod_unthreaded;
+            require MyMod_unthreaded;
+            import MyMod_unthreaded;
         }
     }
 
 Since code that runs both with and without threads is usually pretty
 messy, it's best to isolate the thread-specific code in its own
-module.  In our example above, that's what MyMod_threaded is, and it's
+module.  In our example above, that's what C<MyMod_threaded> is, and it's
 only imported if we're running on a threaded Perl.
 
 =head2 A Note about the Examples
 
-Although thread support is considered to be stable, there are still a number
-of quirks that may startle you when you try out any of the examples below.
 In a real situation, care should be taken that all threads are finished
 executing before the program exits.  That care has B<not> been taken in these
-examples in the interest of simplicity.  Running these examples "as is" will
+examples in the interest of simplicity.  Running these examples I<as is> will
 produce error messages, usually caused by the fact that there are still
 threads running when the program exits.  You should not be alarmed by this.
-Future versions of Perl may fix this problem.
 
 =head2 Creating Threads
 
-The L<threads> package provides the tools you need to create new
+The L<threads> module provides the tools you need to create new
 threads.  Like any other module, you need to tell Perl that you want to use
-it; C<use threads> imports all the pieces you need to create basic
+it; C<use threads;> imports all the pieces you need to create basic
 threads.
 
-The simplest, most straightforward way to create a thread is with new():
+The simplest, most straightforward way to create a thread is with C<create()>:
 
     use threads;
 
-    $thr = threads->new(\&sub1);
+    my $thr = threads->create(\&sub1);
 
     sub sub1 {
-        print "In the thread\n";
+        print("In the thread\n");
     }
 
-The new() method takes a reference to a subroutine and creates a new
-thread, which starts executing in the referenced subroutine.  Control
+The C<create()> method takes a reference to a subroutine and creates a new
+thread that starts executing in the referenced subroutine.  Control
 then passes both to the subroutine and the caller.
 
 If you need to, your program can pass parameters to the subroutine as
 part of the thread startup.  Just include the list of parameters as
-part of the C<threads::new> call, like this:
+part of the C<threads-E<gt>create()> call, like this:
 
     use threads;
 
-    $Param3 = "foo";
-    $thr = threads->new(\&sub1, "Param 1", "Param 2", $Param3);
-    $thr = threads->new(\&sub1, @ParamList);
-    $thr = threads->new(\&sub1, qw(Param1 Param2 Param3));
+    my $Param3 = 'foo';
+    my $thr1 = threads->create(\&sub1, 'Param 1', 'Param 2', $Param3);
+    my @ParamList = (42, 'Hello', 3.14);
+    my $thr2 = threads->create(\&sub1, @ParamList);
+    my $thr3 = threads->create(\&sub1, qw(Param1 Param2 Param3));
 
     sub sub1 {
         my @InboundParameters = @_;
-        print "In the thread\n";
-        print "got parameters >", join("<>", @InboundParameters), "<\n";
+        print("In the thread\n");
+        print('Got parameters >', join('<>', @InboundParameters), "<\n");
     }
 
-
 The last example illustrates another feature of threads.  You can spawn
 off several threads using the same subroutine.  Each thread executes
 the same subroutine, but in a separate thread with a separate
 environment and potentially separate arguments.
 
-C<create()> is a synonym for C<new()>.
+C<new()> is a synonym for C<create()>.
 
 =head2 Waiting For A Thread To Exit
 
 Since threads are also subroutines, they can return values.  To wait
 for a thread to exit and extract any values it might return, you can
-use the join() method:
+use the C<join()> method:
 
     use threads;
 
-    $thr = threads->new(\&sub1);
+    my ($thr) = threads->create(\&sub1);
 
-    @ReturnData = $thr->join;
-    print "Thread returned @ReturnData";
+    my @ReturnData = $thr->join();
+    print('Thread returned ', join(', ', @ReturnData), "\n");
 
-    sub sub1 { return "Fifty-six", "foo", 2; }
+    sub sub1 { return ('Fifty-six', 'foo', 2); }
 
-In the example above, the join() method returns as soon as the thread
+In the example above, the C<join()> method returns as soon as the thread
 ends.  In addition to waiting for a thread to finish and gathering up
-any values that the thread might have returned, join() also performs
+any values that the thread might have returned, C<join()> also performs
 any OS cleanup necessary for the thread.  That cleanup might be
 important, especially for long-running programs that spawn lots of
 threads.  If you don't want the return values and don't want to wait
-for the thread to finish, you should call the detach() method
+for the thread to finish, you should call the C<detach()> method
 instead, as described next.
 
+NOTE: In the example above, the thread returns a list, thus necessitating
+that the thread creation call be made in list context (i.e., C<my ($thr)>).
+See L<threads/"$thr->join()"> and L<threads/"THREAD CONTEXT"> for more
+details on thread context and return values.
+
 =head2 Ignoring A Thread
 
-join() does three things: it waits for a thread to exit, cleans up
+C<join()> does three things: it waits for a thread to exit, cleans up
 after it, and returns any data the thread may have produced.  But what
 if you're not interested in the thread's return values, and you don't
 really care when the thread finishes? All you want is for the thread
 to get cleaned up after when it's done.
 
-In this case, you use the detach() method.  Once a thread is detached,
-it'll run until it's finished, then Perl will clean up after it
+In this case, you use the C<detach()> method.  Once a thread is detached,
+it'll run until it's finished; then Perl will clean up after it
 automatically.
 
     use threads;
 
-    $thr = threads->new(\&sub1); # Spawn the thread
+    my $thr = threads->create(\&sub1);   # Spawn the thread
+
+    $thr->detach();   # Now we officially don't care any more
 
-    $thr->detach; # Now we officially don't care any more
+    sleep(15);        # Let thread run for awhile
 
     sub sub1 {
         $a = 0;
         while (1) {
             $a++;
-            print "\$a is $a\n";
-            sleep 1;
+            print("\$a is $a\n");
+            sleep(1);
         }
     }
 
@@ -311,36 +311,48 @@ Once a thread is detached, it may not be joined, and any return data
 that it might have produced (if it was done and waiting for a join) is
 lost.
 
+C<detach()> can also be called as a class method to allow a thread to
+detach itself:
+
+    use threads;
+
+    my $thr = threads->create(\&sub1);
+
+    sub sub1 {
+        threads->detach();
+        # Do more work
+    }
+
 =head1 Threads And Data
 
 Now that we've covered the basics of threads, it's time for our next
-topic: data.  Threading introduces a couple of complications to data
+topic: Data.  Threading introduces a couple of complications to data
 access that non-threaded programs never need to worry about.
 
 =head2 Shared And Unshared Data
 
-The biggest difference between Perl ithreads and the old 5.005 style
+The biggest difference between Perl I<ithreads> and the old 5.005 style
 threading, or for that matter, to most other threading systems out there,
-is that by default, no data is shared. When a new perl thread is created,
+is that by default, no data is shared. When a new Perl thread is created,
 all the data associated with the current thread is copied to the new
 thread, and is subsequently private to that new thread!
 This is similar in feel to what happens when a UNIX process forks,
 except that in this case, the data is just copied to a different part of
 memory within the same process rather than a real fork taking place.
 
-To make use of threading however, one usually wants the threads to share
+To make use of threading, however, one usually wants the threads to share
 at least some data between themselves. This is done with the
-L<threads::shared> module and the C< : shared> attribute:
+L<threads::shared> module and the C<:shared> attribute:
 
     use threads;
     use threads::shared;
 
-    my $foo : shared = 1;
+    my $foo :shared = 1;
     my $bar = 1;
-    threads->new(sub { $foo++; $bar++ })->join;
+    threads->create(sub { $foo++; $bar++; })->join();
 
-    print "$foo\n";  #prints 2 since $foo is shared
-    print "$bar\n";  #prints 1 since $bar is not shared
+    print("$foo\n");  # Prints 2 since $foo is shared
+    print("$bar\n");  # Prints 1 since $bar is not shared
 
 In the case of a shared array, all the array's elements are shared, and for
 a shared hash, all the keys and values are shared. This places
@@ -352,18 +364,18 @@ assignment will cause the thread to die. For example:
     use threads;
     use threads::shared;
 
-    my $var           = 1;
-    my $svar : shared = 2;
-    my %hash : shared;
+    my $var          = 1;
+    my $svar :shared = 2;
+    my %hash :shared;
 
     ... create some threads ...
 
-    $hash{a} = 1;	# all threads see exists($hash{a}) and $hash{a} == 1
-    $hash{a} = $var	# okay - copy-by-value: same effect as previous
-    $hash{a} = $svar	# okay - copy-by-value: same effect as previous
-    $hash{a} = \$svar	# okay - a reference to a shared variable
-    $hash{a} = \$var	# This will die
-    delete $hash{a}	# okay - all threads will see !exists($hash{a})
+    $hash{a} = 1;       # All threads see exists($hash{a}) and $hash{a} == 1
+    $hash{a} = $var;    # okay - copy-by-value: same effect as previous
+    $hash{a} = $svar;   # okay - copy-by-value: same effect as previous
+    $hash{a} = \$svar;  # okay - a reference to a shared variable
+    $hash{a} = \$var;   # This will die
+    delete($hash{a});   # okay - all threads will see !exists($hash{a})
 
 Note that a shared variable guarantees that if two or more threads try to
 modify it at the same time, the internal state of the variable will not
@@ -378,22 +390,22 @@ number of pitfalls.  One pitfall is the race condition:
     use threads;
     use threads::shared;
 
-    my $a : shared = 1;
-    $thr1 = threads->new(\&sub1);
-    $thr2 = threads->new(\&sub2);
+    my $a :shared = 1;
+    my $thr1 = threads->create(\&sub1);
+    my $thr2 = threads->create(\&sub2);
 
     $thr1->join;
     $thr2->join;
-    print "$a\n";
+    print("$a\n");
 
     sub sub1 { my $foo = $a; $a = $foo + 1; }
     sub sub2 { my $bar = $a; $a = $bar + 1; }
 
-What do you think $a will be? The answer, unfortunately, is "it
-depends." Both sub1() and sub2() access the global variable $a, once
+What do you think C<$a> will be? The answer, unfortunately, is I<it
+depends>. Both C<sub1()> and C<sub2()> access the global variable C<$a>, once
 to read and once to write.  Depending on factors ranging from your
 thread implementation's scheduling algorithm to the phase of the moon,
-$a can be 2 or 3.
+C<$a> can be 2 or 3.
 
 Race conditions are caused by unsynchronized access to shared
 data.  Without explicit synchronization, there's no way to be sure that
@@ -402,17 +414,17 @@ and the time you update it.  Even this simple code fragment has the
 possibility of error:
 
     use threads;
-    my $a : shared = 2;
-    my $b : shared;
-    my $c : shared;
+    my $a :shared = 2;
+    my $b :shared;
+    my $c :shared;
     my $thr1 = threads->create(sub { $b = $a; $a = $b + 1; });
     my $thr2 = threads->create(sub { $c = $a; $a = $c + 1; });
     $thr1->join;
     $thr2->join;
 
-Two threads both access $a.  Each thread can potentially be interrupted
-at any point, or be executed in any order.  At the end, $a could be 3
-or 4, and both $b and $c could be 2 or 3.
+Two threads both access C<$a>.  Each thread can potentially be interrupted
+at any point, or be executed in any order.  At the end, C<$a> could be 3
+or 4, and both C<$b> and C<$c> could be 2 or 3.
 
 Even C<$a += 5> or C<$a++> are not guaranteed to be atomic.
 
@@ -433,48 +445,48 @@ techniques such as queues, which remove some of the hard work involved.
 
 =head2 Controlling access: lock()
 
-The lock() function takes a shared variable and puts a lock on it.
+The C<lock()> function takes a shared variable and puts a lock on it.
 No other thread may lock the variable until the variable is unlocked
 by the thread holding the lock. Unlocking happens automatically
 when the locking thread exits the block that contains the call to the
-C<lock()> function.  Using lock() is straightforward: this example has
+C<lock()> function.  Using C<lock()> is straightforward: This example has
 several threads doing some calculations in parallel, and occasionally
 updating a running total:
 
     use threads;
     use threads::shared;
 
-    my $total : shared = 0;
+    my $total :shared = 0;
 
     sub calc {
-	for (;;) {
-	    my $result;
-	    # (... do some calculations and set $result ...)
-	    {
-		lock($total); # block until we obtain the lock
-		$total += $result;
-	    } # lock implicitly released at end of scope
-	    last if $result == 0;
-	}
+        while (1) {
+            my $result;
+            # (... do some calculations and set $result ...)
+            {
+                lock($total);  # Block until we obtain the lock
+                $total += $result;
+            } # Lock implicitly released at end of scope
+            last if $result == 0;
+        }
     }
 
-    my $thr1 = threads->new(\&calc);
-    my $thr2 = threads->new(\&calc);
-    my $thr3 = threads->new(\&calc);
-    $thr1->join;
-    $thr2->join;
-    $thr3->join;
-    print "total=$total\n";
+    my $thr1 = threads->create(\&calc);
+    my $thr2 = threads->create(\&calc);
+    my $thr3 = threads->create(\&calc);
+    $thr1->join();
+    $thr2->join();
+    $thr3->join();
+    print("total=$total\n");
 
-lock() blocks the thread until the variable being locked is
-available.  When lock() returns, your thread can be sure that no other
+C<lock()> blocks the thread until the variable being locked is
+available.  When C<lock()> returns, your thread can be sure that no other
 thread can lock that variable until the block containing the
 lock exits.
 
 It's important to note that locks don't prevent access to the variable
 in question, only lock attempts.  This is in keeping with Perl's
 longstanding tradition of courteous programming, and the advisory file
-locking that flock() gives you.
+locking that C<flock()> gives you.
 
 You may lock arrays and hashes as well as scalars.  Locking an array,
 though, will not block subsequent locks on array elements, just lock
@@ -482,32 +494,32 @@ attempts on the array itself.
 
 Locks are recursive, which means it's okay for a thread to
 lock a variable more than once.  The lock will last until the outermost
-lock() on the variable goes out of scope. For example:
+C<lock()> on the variable goes out of scope. For example:
 
-    my $x : shared;
+    my $x :shared;
     doit();
 
     sub doit {
-	{
-	    {
-		lock($x); # wait for lock
-		lock($x); # NOOP - we already have the lock
-		{
-		    lock($x); # NOOP
-		    {
-			lock($x); # NOOP
-			lockit_some_more();
-		    }
-		}
-	    } # *** implicit unlock here ***
-	}
+        {
+            {
+                lock($x); # Wait for lock
+                lock($x); # NOOP - we already have the lock
+                {
+                    lock($x); # NOOP
+                    {
+                        lock($x); # NOOP
+                        lockit_some_more();
+                    }
+                }
+            } # *** Implicit unlock here ***
+        }
     }
 
     sub lockit_some_more {
-	lock($x); # NOOP
-    } # nothing happens here
+        lock($x); # NOOP
+    } # Nothing happens here
 
-Note that there is no unlock() function - the only way to unlock a
+Note that there is no C<unlock()> function - the only way to unlock a
 variable is to allow it to go out of scope.
 
 A lock can either be used to guard the data contained within the variable
@@ -526,16 +538,16 @@ Consider the following code:
 
     use threads;
 
-    my $a : shared = 4;
-    my $b : shared = "foo";
-    my $thr1 = threads->new(sub {
+    my $a :shared = 4;
+    my $b :shared = 'foo';
+    my $thr1 = threads->create(sub {
         lock($a);
-        sleep 20;
+        sleep(20);
         lock($b);
     });
-    my $thr2 = threads->new(sub {
+    my $thr2 = threads->create(sub {
         lock($b);
-        sleep 20;
+        sleep(20);
         lock($a);
     });
 
@@ -544,10 +556,10 @@ won't hang is if one of the two threads acquires both locks
 first.  A guaranteed-to-hang version is more complicated, but the
 principle is the same.
 
-The first thread will grab a lock on $a, then, after a pause during which
+The first thread will grab a lock on C<$a>, then, after a pause during which
 the second thread has probably had time to do some work, try to grab a
-lock on $b.  Meanwhile, the second thread grabs a lock on $b, then later
-tries to grab a lock on $a.  The second lock attempt for both threads will
+lock on C<$b>.  Meanwhile, the second thread grabs a lock on C<$b>, then later
+tries to grab a lock on C<$a>.  The second lock attempt for both threads will
 block, each waiting for the other to release its lock.
 
 This condition is called a deadlock, and it occurs whenever two or
@@ -558,8 +570,8 @@ resource is itself waiting for a lock to be released.
 
 There are a number of ways to handle this sort of problem.  The best
 way is to always have all threads acquire locks in the exact same
-order.  If, for example, you lock variables $a, $b, and $c, always lock
-$a before $b, and $b before $c.  It's also best to hold on to locks for
+order.  If, for example, you lock variables C<$a>, C<$b>, and C<$c>, always lock
+C<$a> before C<$b>, and C<$b> before C<$c>.  It's also best to hold on to locks for
 as short a period of time to minimize the risks of deadlock.
 
 The other synchronization primitives described below can suffer from
@@ -575,26 +587,26 @@ this:
     use threads;
     use Thread::Queue;
 
-    my $DataQueue = Thread::Queue->new;
-    $thr = threads->new(sub {
-        while ($DataElement = $DataQueue->dequeue) {
-            print "Popped $DataElement off the queue\n";
+    my $DataQueue = Thread::Queue->new();
+    my $thr = threads->create(sub {
+        while (my $DataElement = $DataQueue->dequeue()) {
+            print("Popped $DataElement off the queue\n");
         }
     });
 
     $DataQueue->enqueue(12);
     $DataQueue->enqueue("A", "B", "C");
     $DataQueue->enqueue(\$thr);
-    sleep 10;
+    sleep(10);
     $DataQueue->enqueue(undef);
-    $thr->join;
+    $thr->join();
 
-You create the queue with C<new Thread::Queue>.  Then you can
-add lists of scalars onto the end with enqueue(), and pop scalars off
-the front of it with dequeue().  A queue has no fixed size, and can grow
+You create the queue with C<Thread::Queue-E<gt>new()>.  Then you can
+add lists of scalars onto the end with C<enqueue()>, and pop scalars off
+the front of it with C<dequeue()>.  A queue has no fixed size, and can grow
 as needed to hold everything pushed on to it.
 
-If a queue is empty, dequeue() blocks until another thread enqueues
+If a queue is empty, C<dequeue()> blocks until another thread enqueues
 something.  This makes queues ideal for event loops and other
 communications between threads.
 
@@ -604,44 +616,44 @@ Semaphores are a kind of generic locking mechanism. In their most basic
 form, they behave very much like lockable scalars, except that they
 can't hold data, and that they must be explicitly unlocked. In their
 advanced form, they act like a kind of counter, and can allow multiple
-threads to have the 'lock' at any one time.
+threads to have the I<lock> at any one time.
 
 =head2 Basic semaphores
 
-Semaphores have two methods, down() and up(): down() decrements the resource
-count, while up increments it. Calls to down() will block if the
+Semaphores have two methods, C<down()> and C<up()>: C<down()> decrements the resource
+count, while up increments it. Calls to C<down()> will block if the
 semaphore's current count would decrement below zero.  This program
 gives a quick demonstration:
 
     use threads;
     use Thread::Semaphore;
 
-    my $semaphore = new Thread::Semaphore;
-    my $GlobalVariable : shared = 0;
+    my $semaphore = Thread::Semaphore->new();
+    my $GlobalVariable :shared = 0;
 
-    $thr1 = new threads \&sample_sub, 1;
-    $thr2 = new threads \&sample_sub, 2;
-    $thr3 = new threads \&sample_sub, 3;
+    $thr1 = threads->create(\&sample_sub, 1);
+    $thr2 = threads->create(\&sample_sub, 2);
+    $thr3 = threads->create(\&sample_sub, 3);
 
     sub sample_sub {
-        my $SubNumber = shift @_;
+        my $SubNumber = shift(@_);
         my $TryCount = 10;
         my $LocalCopy;
-        sleep 1;
+        sleep(1);
         while ($TryCount--) {
-            $semaphore->down;
+            $semaphore->down();
             $LocalCopy = $GlobalVariable;
-            print "$TryCount tries left for sub $SubNumber (\$GlobalVariable is $GlobalVariable)\n";
-            sleep 2;
+            print("$TryCount tries left for sub $SubNumber (\$GlobalVariable is $GlobalVariable)\n");
+            sleep(2);
             $LocalCopy++;
             $GlobalVariable = $LocalCopy;
-            $semaphore->up;
+            $semaphore->up();
         }
     }
 
-    $thr1->join;
-    $thr2->join;
-    $thr3->join;
+    $thr1->join();
+    $thr2->join();
+    $thr3->join();
 
 The three invocations of the subroutine all operate in sync.  The
 semaphore, though, makes sure that only one thread is accessing the
@@ -650,20 +662,21 @@ global variable at once.
 =head2 Advanced Semaphores
 
 By default, semaphores behave like locks, letting only one thread
-down() them at a time.  However, there are other uses for semaphores.
+C<down()> them at a time.  However, there are other uses for semaphores.
 
 Each semaphore has a counter attached to it. By default, semaphores are
-created with the counter set to one, down() decrements the counter by
-one, and up() increments by one. However, we can override any or all
+created with the counter set to one, C<down()> decrements the counter by
+one, and C<up()> increments by one. However, we can override any or all
 of these defaults simply by passing in different values:
 
     use threads;
     use Thread::Semaphore;
+
     my $semaphore = Thread::Semaphore->new(5);
                     # Creates a semaphore with the counter set to five
 
-    $thr1 = threads->new(\&sub1);
-    $thr2 = threads->new(\&sub1);
+    my $thr1 = threads->create(\&sub1);
+    my $thr2 = threads->create(\&sub1);
 
     sub sub1 {
         $semaphore->down(5); # Decrements the counter by five
@@ -671,14 +684,14 @@ of these defaults simply by passing in different values:
         $semaphore->up(5); # Increment the counter by five
     }
 
-    $thr1->detach;
-    $thr2->detach;
+    $thr1->detach();
+    $thr2->detach();
 
-If down() attempts to decrement the counter below zero, it blocks until
+If C<down()> attempts to decrement the counter below zero, it blocks until
 the counter is large enough.  Note that while a semaphore can be created
-with a starting count of zero, any up() or down() always changes the
-counter by at least one, and so $semaphore->down(0) is the same as
-$semaphore->down(1).
+with a starting count of zero, any C<up()> or C<down()> always changes the
+counter by at least one, and so C<$semaphore->down(0)> is the same as
+C<$semaphore->down(1)>.
 
 The question, of course, is why would you do something like this? Why
 create a semaphore with a starting count that's not one, or why
@@ -721,29 +734,29 @@ processor-intensive and want to make sure that the user-interface thread
 gets called frequently.  Regardless, there are times that you might want
 a thread to give up the processor.
 
-Perl's threading package provides the yield() function that does
-this. yield() is pretty straightforward, and works like this:
+Perl's threading package provides the C<yield()> function that does
+this. C<yield()> is pretty straightforward, and works like this:
 
     use threads;
 
     sub loop {
-	my $thread = shift;
-	my $foo = 50;
-	while($foo--) { print "in thread $thread\n" }
-	threads->yield;
-	$foo = 50;
-	while($foo--) { print "in thread $thread\n" }
+        my $thread = shift;
+        my $foo = 50;
+        while($foo--) { print("In thread $thread\n"); }
+        threads->yield();
+        $foo = 50;
+        while($foo--) { print("In thread $thread\n"); }
     }
 
-    my $thread1 = threads->new(\&loop, 'first');
-    my $thread2 = threads->new(\&loop, 'second');
-    my $thread3 = threads->new(\&loop, 'third');
+    my $thr1 = threads->create(\&loop, 'first');
+    my $thr2 = threads->create(\&loop, 'second');
+    my $thr3 = threads->create(\&loop, 'third');
 
-It is important to remember that yield() is only a hint to give up the CPU,
+It is important to remember that C<yield()> is only a hint to give up the CPU,
 it depends on your hardware, OS and threading libraries what actually happens.
 B<On many operating systems, yield() is a no-op.>  Therefore it is important
 to note that one should not build the scheduling of the threads around
-yield() calls. It might work on your platform but it won't work on another
+C<yield()> calls. It might work on your platform but it won't work on another
 platform.
 
 =head1 General Thread Utility Routines
@@ -755,84 +768,88 @@ really fit in anyplace else.
 
 =head2 What Thread Am I In?
 
-The C<< threads->self >> class method provides your program with a way to
+The C<threads-E<gt>self()> class method provides your program with a way to
 get an object representing the thread it's currently in.  You can use this
 object in the same way as the ones returned from thread creation.
 
 =head2 Thread IDs
 
-tid() is a thread object method that returns the thread ID of the
+C<tid()> is a thread object method that returns the thread ID of the
 thread the object represents.  Thread IDs are integers, with the main
-thread in a program being 0.  Currently Perl assigns a unique tid to
+thread in a program being 0.  Currently Perl assigns a unique TID to
 every thread ever created in your program, assigning the first thread
 to be created a tid of 1, and increasing the tid by 1 for each new
-thread that's created.
+thread that's created.  When used as a class method, C<threads-E<gt>tid()>
+can be used by a thread to get its own TID.
 
 =head2 Are These Threads The Same?
 
-The equal() method takes two thread objects and returns true
+The C<equal()> method takes two thread objects and returns true
 if the objects represent the same thread, and false if they don't.
 
-Thread objects also have an overloaded == comparison so that you can do
+Thread objects also have an overloaded C<==> comparison so that you can do
 comparison on them as you would with normal objects.
 
 =head2 What Threads Are Running?
 
-C<< threads->list >> returns a list of thread objects, one for each thread
+C<threads-E<gt>list()> returns a list of thread objects, one for each thread
 that's currently running and not detached.  Handy for a number of things,
-including cleaning up at the end of your program:
+including cleaning up at the end of your program (from the main Perl thread,
+of course):
 
     # Loop through all the threads
-    foreach $thr (threads->list) {
-        # Don't join the main thread or ourselves
-        if ($thr->tid && !threads::equal($thr, threads->self)) {
-            $thr->join;
-        }
+    foreach my $thr (threads->list()) {
+        $thr->join();
     }
 
 If some threads have not finished running when the main Perl thread
 ends, Perl will warn you about it and die, since it is impossible for Perl
-to clean up itself while other threads are running
+to clean up itself while other threads are running.
+
+NOTE:  The main Perl thread (thread 0) is in a I<detached> state, and so
+does not appear in the list returned by C<threads-E<gt>list()>.
 
 =head1 A Complete Example
 
 Confused yet? It's time for an example program to show some of the
 things we've covered.  This program finds prime numbers using threads.
 
-    1  #!/usr/bin/perl -w
-    2  # prime-pthread, courtesy of Tom Christiansen
-    3
-    4  use strict;
-    5
-    6  use threads;
-    7  use Thread::Queue;
-    8
-    9  my $stream = new Thread::Queue;
-    10 my $kid    = new threads(\&check_num, $stream, 2);
-    11
-    12 for my $i ( 3 .. 1000 ) {
-    13     $stream->enqueue($i);
-    14 }
+     1 #!/usr/bin/perl
+     2 # prime-pthread, courtesy of Tom Christiansen
+     3
+     4 use strict;
+     5 use warnings;
+     6
+     7 use threads;
+     8 use Thread::Queue;
+     9
+    10 my $stream = Thread::Queue->new();
+    11 for my $i ( 3 .. 1000 ) {
+    12     $stream->enqueue($i);
+    13 }
+    14 $stream->enqueue(undef);
     15
-    16 $stream->enqueue(undef);
-    17 $kid->join;
+    16 threads->create(\&check_num, $stream, 2);
+    17 $kid->join();
     18
     19 sub check_num {
     20     my ($upstream, $cur_prime) = @_;
     21     my $kid;
-    22     my $downstream = new Thread::Queue;
-    23     while (my $num = $upstream->dequeue) {
-    24         next unless $num % $cur_prime;
+    22     my $downstream = Thread::Queue->new();
+    23     while (my $num = $upstream->dequeue()) {
+    24         next unless ($num % $cur_prime);
     25         if ($kid) {
-    26            $downstream->enqueue($num);
-    27          	} else {
-    28            print "Found prime $num\n";
-    29	              $kid = new threads(\&check_num, $downstream, $num);
+    26             $downstream->enqueue($num);
+    27         } else {
+    28             print("Found prime $num\n");
+    29             $kid = threads->create(\&check_num, $downstream, $num);
     30         }
     31     }
-    32     $downstream->enqueue(undef) if $kid;
-    33     $kid->join		if $kid;
-    34 }
+    32     if ($kid) {
+    33         $downstream->enqueue(undef);
+    34         $kid->join();
+    35     }
+    36 }
 
 This program uses the pipeline model to generate prime numbers.  Each
 thread in the pipeline has an input queue that feeds numbers to be
@@ -846,9 +863,9 @@ pipeline.
 This probably sounds a bit more confusing than it really is, so let's
 go through this program piece by piece and see what it does.  (For
 those of you who might be trying to remember exactly what a prime
-number is, it's a number that's only evenly divisible by itself and 1)
+number is, it's a number that's only evenly divisible by itself and 1.)
 
-The bulk of the work is done by the check_num() subroutine, which
+The bulk of the work is done by the C<check_num()> subroutine, which
 takes a reference to its input queue and a prime number that it's
 responsible for.  After pulling in the input queue and the prime that
 the subroutine's checking (line 20), we create a new queue (line 22)
@@ -866,17 +883,18 @@ new thread if we haven't.
 The new thread creation is line 29.  We pass on to it a reference to
 the queue we've created, and the prime number we've found.
 
-Finally, once the loop terminates (because we got a 0 or undef in the
-queue, which serves as a note to die), we pass on the notice to our
+Finally, once the loop terminates (because we got a 0 or C<undef> in the
+queue, which serves as a note to terminate), we pass on the notice to our
 child and wait for it to exit if we've created a child (lines 32 and
-37).
+35).
 
-Meanwhile, back in the main thread, we create a queue (line 9) and the
-initial child thread (line 10), and pre-seed it with the first prime:
-2.  Then we queue all the numbers from 3 to 1000 for checking (lines
-12-14), then queue a die notice (line 16) and wait for the first child
-thread to terminate (line 17).  Because a child won't die until its
-child has died, we know that we're done once we return from the join.
+Meanwhile, back in the main thread, we first create a queue (line 10) and
+queue up all the numbers from 3 to 1000 for checking (lines 11-13),
+plus a termination notice (line 14).  Then we create the initial child
+threads (line 16), passing it the queue and the first prime: 2.  Finally,
+we wait for the first child thread to terminate (line 17).  Because a
+child won't terminate until its child has terminated, we know that we're
+done once we return from the C<join()>.
 
 That's how it works.  It's pretty simple; as with many Perl programs,
 the explanation is much longer than the program.
@@ -894,7 +912,7 @@ far as it's concerned, your process is just a process.
 This is the easiest way to implement threads, and the way most OSes
 start.  The big disadvantage is that, since the OS knows nothing about
 threads, if one thread blocks they all do.  Typical blocking activities
-include most system calls, most I/O, and things like sleep().
+include most system calls, most I/O, and things like C<sleep()>.
 
 Kernel threads are the next step in thread evolution.  The OS knows
 about kernel threads, and makes allowances for them.  The main
@@ -912,8 +930,8 @@ though, regardless of how many CPUs a system might have.
 Since kernel threading can interrupt a thread at any time, they will
 uncover some of the implicit locking assumptions you may make in your
 program.  For example, something as simple as C<$a = $a + 2> can behave
-unpredictably with kernel threads if $a is visible to other
-threads, as another thread may have changed $a between the time it
+unpredictably with kernel threads if C<$a> is visible to other
+threads, as another thread may have changed C<$a> between the time it
 was fetched on the right hand side and the time the new value is
 stored.
 
@@ -952,13 +970,13 @@ Most modern operating systems support preemptive multitasking nowadays.
 
 =head1 Performance considerations
 
-The main thing to bear in mind when comparing ithreads to other threading
+The main thing to bear in mind when comparing Perl's I<ithreads> to other threading
 models is the fact that for each new thread created, a complete copy of
-all the variables and data of the parent thread has to be taken. Thus
+all the variables and data of the parent thread has to be taken. Thus,
 thread creation can be quite expensive, both in terms of memory usage and
 time spent in creation. The ideal way to reduce these costs is to have a
 relatively short number of long-lived threads, all created fairly early
-on -  before the base thread has accumulated too much data. Of course, this
+on -- before the base thread has accumulated too much data. Of course, this
 may not always be possible, so compromises have to be made. However, after
 a thread has been created, its performance and extra memory usage should
 be little different than ordinary code.
@@ -973,33 +991,37 @@ Perl data is thread-private unless explicitly shared, the threads can
 affect process-scope state, affecting all the threads.
 
 The most common example of this is changing the current working
-directory using chdir().  One thread calls chdir(), and the working
+directory using C<chdir()>.  One thread calls C<chdir()>, and the working
 directory of all the threads changes.
 
-Even more drastic example of a process-scope change is chroot():
+Even more drastic example of a process-scope change is C<chroot()>:
 the root directory of all the threads changes, and no thread can
-undo it (as opposed to chdir()).
+undo it (as opposed to C<chdir()>).
 
-Further examples of process-scope changes include umask() and
+Further examples of process-scope changes include C<umask()> and
 changing uids/gids.
 
-Thinking of mixing fork() and threads?  Please lie down and wait
-until the feeling passes.  Be aware that the semantics of fork() vary
+Thinking of mixing C<fork()> and threads?  Please lie down and wait
+until the feeling passes.  Be aware that the semantics of C<fork()> vary
 between platforms.  For example, some UNIX systems copy all the current
 threads into the child process, while others only copy the thread that
-called fork(). You have been warned!
+called C<fork()>. You have been warned!
 
-Similarly, mixing signals and threads should not be attempted.
+Similarly, mixing signals and threads may be problematic.
 Implementations are platform-dependent, and even the POSIX
 semantics may not be what you expect (and Perl doesn't even
-give you the full POSIX API).
+give you the full POSIX API).  For example, there is no way to
+guarantee that a signal sent to a multi-threaded Perl application
+will get intercepted by any particular thread.  (However, a recently
+added feature does provide the capability to send signals between
+threads.  See L<threads/"THREAD SIGNALLING> for more details.)
 
 =head1 Thread-Safety of System Libraries
 
 Whether various library calls are thread-safe is outside the control
 of Perl.  Calls often suffering from not being thread-safe include:
-localtime(), gmtime(), get{gr,host,net,proto,serv,pw}*(), readdir(),
-rand(), and srand() -- in general, calls that depend on some global
+C<localtime()>, C<gmtime()>, C<get{gr,host,net,proto,serv,pw}*()>, C<readdir()>,
+C<rand()>, and C<srand()> -- in general, calls that depend on some global
 external state.
 
 If the system Perl is compiled in has thread-safe variants of such
@@ -1014,7 +1036,7 @@ a full snapshot of those databases).  Perl will start with a small
 buffer, but keep retrying and growing the result buffer
 until the result fits.  If this limitless growing sounds bad for
 security or memory consumption reasons you can recompile Perl with
-PERL_REENTRANT_MAXSIZE defined to the maximum number of bytes you will
+C<PERL_REENTRANT_MAXSIZE> defined to the maximum number of bytes you will
 allow.
 
 =head1 Conclusion
@@ -1023,6 +1045,23 @@ A complete thread tutorial could fill a book (and has, many times),
 but with what we've covered in this introduction, you should be well
 on your way to becoming a threaded Perl expert.
 
+=head1 SEE ALSO
+
+Annotated POD for L<threads>:
+L<http://annocpan.org/?mode=search&field=Module&name=threads>
+
+Lastest version of L<threads> on CPAN:
+L<http://search.cpan.org/search?module=threads>
+
+Annotated POD for L<threads::shared>:
+L<http://annocpan.org/?mode=search&field=Module&name=threads%3A%3Ashared>
+
+Lastest version of L<threads::shared> on CPAN:
+L<http://search.cpan.org/search?module=threads%3A%3Ashared>
+
+Perl threads mailing list:
+L<http://lists.cpan.org/showlist.cgi?name=iThreads>
+
 =head1 Bibliography
 
 Here's a short bibliography courtesy of Jürgen Christoffel:
@@ -1094,7 +1133,7 @@ Dan Sugalski E<lt>dan@sidhe.org<gt>
 Slightly modified by Arthur Bergman to fit the new thread model/module.
 
 Reworked slightly by Jörg Walter E<lt>jwalt@cpan.org<gt> to be more concise
-about thread-safety of perl code.
+about thread-safety of Perl code.
 
 Rearranged slightly by Elizabeth Mattijsen E<lt>liz@dijkmat.nl<gt> to put
 less emphasis on yield().
@@ -1106,4 +1145,4 @@ Journal #10, and is copyright 1998 The Perl Journal. It appears courtesy
 of Jon Orwant and The Perl Journal.  This document may be distributed
 under the same terms as Perl itself.
 
-For more information please see L<threads> and L<threads::shared>.
+=cut