Environment modules is used to selectively choose which version of programs to load into the environment. It is commonly used on HPC clusters. It is included in ports as sysutils/modules

The stock installation of sysutils/modules includes a configuration file: /usr/local/Modules/3.1.6/init/.modulespath

This is what is in the file:

#
#  @(#).modulespath.in	1.3\t95/08/06  
#  Module version 3.1.6
#
#  Modulepath initial setup
#  ========================
#
#  This file defines the initial setup for the module files search path.
#  Comments may be added anywhere. The begin on # and continue until the 
#     end of the line
#  Each line containing a single path will be added to the MODULEPATH
#     environment variable. You may add as many as you want - just
#     limited by the variable size of your shell.
#

/usr/local/Modules/versions					# location of version files
/usr/local/Modules/$MODULE_VERSION/modulefiles		# Module pkg modulefiles
/usr/local/lib/					# General module files
# /usr/local/Modules/3.1.6/your_contribs			# Edit for your requirements


If you try to add a new path to the list (at the bottom), the program segfaults and dumps a core in the current directory.

Fix: 

The problem is that /usr/local/lib is getting added as a location for possible new module definitions. Something in the parsing of /usr/local/lib is causing the program to segfault.

Commenting out /usr/local/lib solves the problem.
How-To-Repeat: Install sysutils/modules, add a new path to the end of the .modulepath file. Run 'module avail'. (Modules is usually setup as part of a shell function, to test it directly, run '/usr/local/Modules/3.1.6/bin/modulecmd bash avail` (or zsh, or tcsh, etc...).