Unable to use ignore-re with start regex "^"

[alexander-schranz]

I think I'm missing something maybe escaping or something but I try to use:

html5validator index.html --ignore-re "^CSS: "

or

html5validator index.html --ignore-re "/^CSS: /"

to filter out messages like:

CSS: 'margin-block-end': Property 'margin-block-end' doesn't exist.

But both seems not to work I know something like CSS: works but that would also filter out messages when CSS: would be part of that message and not the start of the message. Maybe I just miss how I need to escape ^ correctly.