It works for me as posted. I added a couple of trace lines to convince myself: 

[ 0:29:23.03]C:\test>670431.pl
thread 1 started
thread 2 started
thread 3 started
thread 4 started
thread 5 started
thread 6 started
thread 7 started
thread 9 started
thread 8 started
thread 10 started
[SNIP]
thread 474 ended
thread 244 ended
thread 239 ended
thread 496 started
thread 497 started
thread 498 started
thread 499 started
If you can read this line, I have run to completion and failed to fail
+.  Which makes my success a failure.  I'm so emo.

[download]

As you are detaching the threads, they weren't all able to complete before the main thread ended.

So rather than all that stuff above, how about posting some useful information like the versions of the modules you are using. Particularly threads

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In reply to Re: ithreads picks fight with LWP::Agent; everybody loses (Works for me!) by BrowserUk
in thread ithreads picks fight with LWP::Agent; everybody loses by BlairHippo

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