Why anyone would want to spider CPANdeps is beyond me, but a load of idiots in the Ukraine do want to, and their bot, as well as ignoring robots.txt (just like all the other search engines in the entire world, it seems) sends requests as fast as it can. All the timeouts and the errors about CPANdeps running out of database connections must mean they get some really high quality data.
All fixed though:
/sbin/iptables -A INPUT -s 126.96.36.199/19 -j DROP
/sbin/iptables -A INPUT -s 188.8.131.52/19 -j DROP
If this inconveniences any Ukrainian perl hackers, then I apologise. You should address your complaints to the employees of ahrefs.com, preferably attached to baseball bats, knives and guns.