--- AnyEvent/lib/AnyEvent.pm	2008/05/10 00:45:18	1.109
+++ AnyEvent/lib/AnyEvent.pm	2008/05/10 01:04:42	1.112
@@ -551,12 +551,16 @@
 have created an AnyEvent watcher anyway, that is, as late as possible at
 runtime.
 
-=item AnyEvent::on_detect { BLOCK }
+=item $guard = AnyEvent::post_detect { BLOCK }
 
 Arranges for the code block to be executed as soon as the event model is
 autodetected (or immediately if this has already happened).
 
-=item @AnyEvent::on_detect
+If called in scalar or list context, then it creates and returns an object
+that automatically removes the callback again when it is destroyed. See
+L<Coro::BDB> for a case where this is useful.
+
+=item @AnyEvent::post_detect
 
 If there are any code references in this array (you can C<push> to it
 before or after loading AnyEvent), then they will called directly after
@@ -566,7 +570,7 @@
 if it contains a true value then the event loop has already been detected,
 and the array will be ignored.
 
-Best use C<AnyEvent::on_detect { BLOCK }> instead.
+Best use C<AnyEvent::post_detect { BLOCK }> instead.
 
 =back
 
@@ -718,16 +722,28 @@
 
 our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
 
-our @on_detect;
+our @post_detect;
+
+sub post_detect(&) {
+   my ($cb) = @_;
 
-sub on_detect(&) {
    if ($MODEL) {
-      $_[0]->();
+      $cb->();
+
+      1
    } else {
-      push @on_detect, $_[0];
+      push @post_detect, $cb;
+
+      defined wantarray
+         ? bless \$cb, "AnyEvent::Util::Guard"
+         : ()
    }
 }
 
+sub AnyEvent::Util::Guard::DESTROY {
+   @post_detect = grep $_ != ${$_[0]}, @post_detect;
+}
+
 sub detect() {
    unless ($MODEL) {
       no strict 'refs';
@@ -777,7 +793,7 @@
       unshift @ISA, $MODEL;
       push @{"$MODEL\::ISA"}, "AnyEvent::Base";
 
-      (shift @on_detect)->() while @on_detect;
+      (shift @post_detect)->() while @post_detect;
    }
 
    $MODEL