Original grep was pretty much a wrapper around sed (or actually maybe ed, I don’t remember). That’s why it’s called g/re/p, which is the sed command to do the same thing.

HTML is not even a tree (XHTML is. XML is a type 2 grammar). SGML languages like HTML are more similar to Tree-adjoining grammars.

For example <b>This<i>is perfectly</b>valid</i> html.

If it’s a verb it should be a button, not a toggle

So looking at it it has no resemblance to python syntax, but it does use typical python library semantics.

I couldn’t even get Qt Creator or KDevelop

Honestly this sounds wild to me, I’ve never had Qt Creator fail on me. Do you use a distro that doesn’t distribute headers with packages?