Calling all #regex witches and warlocks!

I want to match individually each space at the beginning of each line of the input text. I do not want to match any other space.

Text input:

Baseline of this text
  Indentation with two spaces
    Surprise, the text has two  spaces too!

Target syntax: PCRE2 (PHP >= 7.3)
Expected matches: 6So far my best attempt is /(?<=^| ) /m but it also matches spaces beyond the first in any series of two or more consecutive spaces anywhere in the text, not just at the beginning of each line. See https://regex101.com/r/GXfJL0/1

Can you do better?