async BLOCK;
        "async" creates a thread to execute the block immediately following
        it. This block is treated as an anonymous subroutine, and so must have
        a semicolon after the closing brace.

##</code><code>##

Threads are implemented in a way that make them easy to misuse.
Few people know how to use them correctly or will be able to provide help.

The use of interpreter-based threads in perl is officially discouraged.