in reply to Things you need to know before programming Perl ithreads

use threads (); my $thread; BEGIN { # execute this at compile time $thread = threads->new( sub { print "Benchmark has not been loaded!\n" unless defined $Bench +mark::VERSION; # do your Benchmark stuff } ); } use Benchmark; $thread->join;
which prints:
Benchmark has not been loaded!
Scalars leaked: 1
Yikes! What is that! "Scalars leaked: 1". Well, yes, that's one of the remaining problems/features/bugs of the Perl ithreads implementation. This particularly seems to happen when you start threads at compile time. From practical experience, I must say it seems to be pretty harmless.
The leaked scalar is the result of returning a closure from a thread. In many cases it is, as mentioned, harmless. However, in some implementations of Perl, returning a closure from a thread may cause the interpreter to crash (i.e., dump core). Caveat emptor.

Remember: There's always one more bug.