There is another place that provides useful information about Perl threads. Checkout the document for Thread module, it talks about a bit history, and more importantly, what you want to know about installation.

I copy and paste a little piece of it:

“Neither model is configured by default into Perl (except, as mentioned above, in Win32 ithreads are always available.) You can see your Perl's threading configuration by running perl -V and looking for the use...threads variables, or inside script by use Config; and testing for $Config{use5005threads} and $Config{useithreads}.”

And made up a three-line to do what they said:

use Config;
print "use 5005 threads\n" if $Config{use5005threads};
print "use ithreads\n" if $Config{useithreads};
[download]

Hope this helps.