TL;DR: mv ~/perl5 ~/perl5.bak should restore scripts such as cpan that depend on List::Util but get the version compiled for older version of Perl from ~/perl5.

This has happened because Debian Jessie has Perl v5.20, Debian Stretch has v5.24, both Perls expect their modules to be in ~/perl5 (probably via local::lib) but are binary incompatible. It is likely that you have the compatible version of List::Util (and other cpan dependencies) installed somewhere in /usr, but modules installed via local::lib take precedence and manage to crash the interpreter before it can use right one.

One your Perl installation works, you can visit ~/perl5.bak to see which modules you would need to install again, for the new version of Perl.