Foreman uses common ERB style templating. Foreman templates consists of a mixture of Bash scripts and appropriate macros and functions. You can find a list of built-in macros and functions here. Within such macro you can use further Ruby code. For example to extract the last digits og an IP address you can use the following macro:
Where @host.ip is a built-in macro in Foreman (see link above), to_s is Ruby code and means “convert into string”, split wherever you find a “.” and read the output reverse and take the last value (“-1”).
If you want to check if a template will render correctly for an appropriate host you can open your template in your browser: