2 # Matches the header part
3 (?:Content- # start of content header
4 (?:Type: (?>\s*) # rest of c/t header
5 [\w-]+/[\w-]+ # content-type (any)
6 |Disposition: (?>\s*) # content-disposition hdr
7 attachment) # content-disposition
8 ;(?>\s*) # ; space or newline
9 (?:file)?name= # filename=/name=
10 |begin (?>\s+) [0-7]{3,4} (?>\s+)) # begin octal-mode