perl - Regex for specific file structure -

i need parse file next simple structure:

some string 1 string 2 string 3  string x string y string z ... 

file consist of 2 parts separated "\n\n" or "\r\n\r\n". separator present in example after "some string 3". each part optional, if first part omitted there 1(but regex need 2 empty lines) empty line(\n|\r\n) before second part. , if second part omitted there number of empty lines after first part(include no empty lines @ all).

i'm trying achieve desired result regex this:

(?isx: \h* (.+)? \h* (?:(?:\n|\r\n){2,} \h* (.+))? \s*) 

but no success because first "(.+)?" greedy , if making 2nd part non-optional violates requirements both part must optional. know can use split /(?:\n|\r\n)/, $str in case file in future have more complex structure can't use split.

can me this?

you might want use non-greedy group, since don't want match seperator.

(?ìsx: (?:        (.*?)          # non greedy        (?:\r?\n){2,}  # matches \r\n\n might not of concern        |\r?\n)        # 1 empty line.        (.*)           # second group ) 

i don't know wanted achieve \hs. if want ensure there in lines (right now, . match \n or spaces) try (?:[^\n]+\n)*? groups.

also, brevities sake, avoided explicit ? used. there might difference in results. if match nothing under star, you'll empty string, if don't match @ all, value of group-variable undefined. here short example show difference:

"aa" =~ /(c)?(d*)aa/ 

here $1 undefined, while $2 empty string. minor difference might yield annoying warnings or unexpected results if tested defined contents of group.