Programming Language and Development IDE
The search software is written in C# under Visual Studio Code (VSCode). I find 'namespaces' in C# a really intuitive way of structuring re-useable code.
Another feature I like in VSCode is the seamless integration with GitHub. Committing changes with messages is a simple process (although I do confess to being lazy by creating cryptic messages) and uploading to GitHub is just a mouse click. Even initialising repositories on GitHub can quickly and easily done within VSCode.
A caveat to this is that it took a lot of head-scratching to initially get it all working (initially figuring out how to set up project files for C# was a pain). To simplify creating new projects I use edited clones of old projects cut-and-pasted to create new ones.
The search code was developed first to work on single files and then expanded to process blocks of files.