Ignore that shit. It literally came about because unix users on got tired of not helping with threading questions. People who never tried threads agreed a scary warnings
https://www.nntp.perl.org/group/perl.perl5.porters/2014/03/msg213382.html
Its self-admitted FEARmongering from irc burnouts -- we're tired of trying to discourage folks from using threads and how to use threads on the irc .... lets scare them in the documentation .... it doesn't belong
Well see
Re^2: Splitting large array for threads. and follow deep, basically using threads has caveats so we'll misuse the "discouraged" label ... dumb
Subject: PATCH add discouragement warning to perl threads documentation
The common reactions to someone asking for help with threads even in #p5p
being: "You're doing it wrong!" or "You have brain damage!" This commit
attempts to reduce the number of such incidences by putting a huge warning
on the threads documentation that should discourage all but the most
determined.