Perl threads are not ready for Prime Time.

What does that mean? Who said it? And how will you know unless you try it?

threads::shared says it:

       BUGS
       bless is not supported on shared references. In the current 
       version, bless will only bless the thread local reference and 
       the blessing will not propagate to the other threads. 
       This is expected to be implemented in a future version 
       of Perl.

       Does not support splice on arrays!

       Taking references to the elements of shared arrays and hashes 
       does not autovivify the elements, and neither does slicing a 
       shared array/hash over non-existent indices/keys autovivify 
       the elements.

       share() allows you to share $hashref->{key} without giving any 
       error message. But the $hashref->{key} is not shared, causing 
       the error "locking can only be used on shared values" to occur
       when you attempt to lock $hasref->{key}.
[download]

DBI says it:

       Threads and Thread Safety

       (...)

       Using DBI with perl threads is not yet recommended for producti
+on envi-
       ronments. For more information see <http://www.perl-
       monks.org/index.pl?node_id=288022>
[download]

liz says it on PerlMonks: 288022 (the node referenced by DBI above).

rt.perl.org says it.

Considering those references, I wouldn't feel comfortable using Perl ithreads in an application designed to accomodate high transaction volumes. I understand that there have been a lot of fixes to ithreads since 5.8.1 (current at the time of liz's post), but there's still no COW. That alone makes it very undesireable.