Scripts are loaded and unloaded with /perl, /python, /ruby and /lua commands (type /help in WeeChat for help about commands).
Examples:
Load a Perl script:
/perl load /tmp/test.pl
List all loaded Perl scripts:
/perl
Load a Python script:
/python load /tmp/test.py
List all loaded Python scripts:
/python
Load a Ruby script:
/ruby load /tmp/test.rb
List all loaded Ruby scripts:
/ruby
Load a Lua script:
/lua load /tmp/test.lua
List all loaded Lua scripts:
/lua