I need help decoding this regular expression from sprockets

Question

I need help decoding this regular expression from sprockets. I am not sure what this matches but if someone give give me some hints or starting points.

HEADER_PATTERN = /
\A (
  (?m:\s*) (
   (\/\* (?m:.*?) \*\/) |
   (\#\#\# (?m:.*?) \#\#\#) |
   (\/\/ .* \n?)+ |
   (\# .* \n?)+
  )
 )+
/x