"°) came into core with 5.20.0 i.e. since May 27, 2014. So only new for oldies like me ;-)"
Just noting that https://perldoc.perl.org/5.20.0/List::Util confirms this; however,
https://perldoc.perl.org/5.34.1/List::Util has "Since version 1.29."
for both pairgrep and pairmap.
I recalled doing some limited investigation into this last month: "Re: Dancer app works until I run it with Plack::Handler::Apache2"
(see the last two dot points under "Other suggestions:").
I now note that https://perldoc.perl.org/5.34.1/List::Util#KNOWN-BUGS lists
while https://perldoc.perl.org/5.20.0/List::Util#KNOWN-BUGS does not.
There are quite a few other functions with "Since version 1.xx." —
probably worth checking when List::Util is used; especially if bugs are detected
or unexpected behaviours are encountered.