It is relatively common to want to customise the contents of the generated
test files to set up custom environment things on an all-scripts basis,
rather than file by file (using =begin SETUP blocks).
Test::Inline::Content::Simple lets you use a very simple Template Toolkit
style template to define this information.
It contains only two tags, plan and tests.
The plan tag will be inserted as either tests = 123> or no_plan.
The tests tag will be replaced by the actual testing code.