m/^([^\s]+) 	# 1st field
	\s
	([^\s]+)		# 2nd
	\s
	([^\s]+)		# 3rd
	\s
	\[([^\]]+)\]	# 4th
	\s
	"([^"]+)"		# 5th
	\s
	([^\s]+)		# etc.
	\s
	([^\s]+)
	\s
	([^\s]+)
	\s
	"([^"]+)"
	/x;

or in regular format:

m/^([^\s]+)\s([^\s]+)\s([^\s]+)\s\[([^\]]+)\]\s"([^"]+)"\s([^\s]+)\s([^\s]+)\s([^\s]+)\s"([^"]+)"/;

Note: if you have any doubts, the following RE was tested on an 18725 line file and successfully parsed all lines.