in reply to Re^2: create new threads inside a thread
in thread create new threads inside a thread

The bug report contains two workarounds. 1) to add 
@_=()

[download]
and 2) to upgrade to bleadperl later than e81cd4d2c506bfc28460d324d94b81010f5ee455 (5.12)

In Section Seekers of Perl Wisdom