OpenIndiana Distribution

After installing the package desktop/office/libreoffice on one of my systems, I got this peculiar behavior:

$ man -l cat
No manual entry for cat
$ env | grep MANPATH
MANPATH=::

This environment setting seems to originate with the file /etc/profile.d/modules.sh that is sourced by every login shell, and contains these lines:

MANPATH='::'
export MANPATH

Setting the manual path variable to two colons seems to confuse the man command. What is the script attempting to do? It's delivered in the package/environment-modules package, by the way.