From threads POD:

END blocks in threads

It is possible to add END blocks to threads by using require or eval w
+ith the 
appropriate code. These END blocks will then be executed when the thre
+ad's 
interpreter is destroyed (i.e., either during a ->join() call, or at p
+rogram 
termination).

However, calling any the threads manpage methods in such an END block 
+will most 
likely fail (e.g., the application may hang, or generate an error) due
+ to 
mutexes that are needed to control functionality within the the thread
+s 
manpage module.

For this reason, the use of END blocks in threads is strongly discoura
+ged.
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