I used to use "do" as a prefix e.g. "doBackup"

Nowadays, I tend to skip using a personal prefix and just try to name commands with a suitable verb in front (e.g. "backupMySQL") and ensure that there's no name collisions.

Whenever I see "my" as a prefix, it feels like such a childish "my first Sony" thing. I hate official sites using that.

This was actually the same feeling I had when I tried to learn perl. I just had a visceral dislike for "my" as the keyword to declare a local variable.

That’s a more meaningful prefix than “,” at the expense of a couple more key strokes. I consider that to still be a win in the book of tab completions.

I would replace underscore with “-“ or “.”

I'd warn against creating files starting with "-" as that can lead to unexpected results with tools if you forget to use "--" to end options. Nothing wrong with using "my-" as a prefix though.