in reply to Re^3: singleton lock not reliable
in thread singleton lock not reliable

Good point. I was mostly trying to point out that using a complicated solution like Docker is a bit much for such a simple problem.

perl -e 'use Crypt::Digest::SHA256 qw[sha256_hex]; print substr(sha256_hex("the Answer To Life, The Universe And Everything"), 6, 2), "\n";'

In Section Seekers of Perl Wisdom