What is a glue language?
architecture, perl, python, scripting
Solution
This is similar to the original meaning of a scripting language and fits the UNIX philosophy of combining many small general-purpose tools to create specialized applications:
You do not write the complete application in the language, but rather, you use the language to orchestrate modules written in (possibly many different) other languages, making them work together to form the application. A glue language makes it easy to do that (convenient syntax, good support for inter-process communication and data munging, no compilation step etc).
Problem
First off, here is one my favorite, and relevant XKCDs: I often hear of people mentioning Perl or Python as "glue" languages. I understand that being scripting languages has something to do with it. Can you explain what it means to use a glue language, and why these languages are good for this purpose?