Needs test with template with multiple {{name}} ( or similar ). Some solutions might replace only one name.

Thanks for the neat kata!
Just a quick note: there’s a small typo in the test cases — “parram” should be “param.”
Also, the phrase “have to filled by two parram function pattern” could be clearer as “should be filled by a two‑param function pattern.”
Great concept overall!

Python & Javascript & Ruby:

• Should test for non-existent tag names in the random tests as well

• Should test for random tag names in the random tests instead of just "{{name}}" and "{{stuff}}" / "{{thing}}"

Note that you did not provide any initial values, which is generally a bad idea if you're really about functional programming.

Needs random tests

Please consider clarifying what to return when the 'pattern' is undefined in Javascript. It's not described in the description, so users have to blindly run test code to figure out a 'null' is required.