In the Python web world, the debate on whether templating languages should offer programming language type abilities has reared its head again. from "Stupid templating languages", to "Not So Stupid Template Languages", "In Response to "Stupid Template Languages"", and discussed more on reddit here.
In the world of Electronic Design Automation and integrating complex EDA software tools, the EDA companies,, on the whole, have embraced TCL as their scripting tool, but sometimes I have inherited a complex design flow, where, to add control, and later flexibility within that control, proprietary initialization file formats and their parsers have grown by adding their own macro language type features and grown to need the power of something like the bash shell. Rather than ditching their proprietary lashed-together, one-off languages for something that is tried and tested and used/debugged by many - such as bash/python/Tcl/Lua they persevere by adding more capability to an in-house, one project language.
In the case of web templating the main argument is that given an intelligent web templating language, people are apt to migrate what should be business logic into the templates thereby muddying the separation of the business logic from the presentation layer. In the EDA field the problem is often the maintenance of the proprietary macro language and the proliferation of languages with which one needs to be familiar with in order to master a design environment.
I won't comment more on the web templating debate, but when it comes to initialization file formats and or initialization scripts then you should stick to pre-existing standards such as .ini files or .csv files in the simpler cases, or use pre-existing scripting languages when you need more power such as bash scripts, Python, or Tcl.