Perhaps I'm too much of a C++ hacker, but I tend to use this capability heavily. Consider a Foo::Lock class which implements a lock on a Foo, where foo might be a file, database record, etc. Then, your methods inside Foo.pm can be made "safe" by code like:

sub do_something()
{
   my $obj = shift @_;
   my $crit = new Foo::Lock( $obj );
   $crit->lock();

   # now do something in the critical section ...
   $obj->yada_yada();
   return unless $obj->valid();

   # now do some more stuff...
   $obj->yada_yada();

   return( $result );
}
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In this case, we don't have to free the Lock explicitly, because its DESTROY method does that automagically. And we are never left with a hard-to-track deadlock defect because our app took a fatal somewhere, leaving the Foo accidentally locked. On the other hand, if $crit were cleaned up soonest, we couldn't depend on the critical section being held for as long as we need it.