http://www.perlmonks.org?node_id=190695

Q&A > regular expressions > Apply regex to entire file, not just individual lines ? - Answer contributed by vxp

You might not want to have your WHOLE file in one variable. Depending on the size of the file, it could eat a LOT of your memory. From my own experience, it is usually enough for me to do $/ = '\n\n' and then the linebreak is 2 new lines, not one. I was parsing a bounce file when I was doing this, which was about 300megs in size, daily. thats a LONG 300mb line. $/ = '\n\n'; took care of it. i ended up with having.. smaller big lines, and was able to do what I wanted to do without consuming a lot of RAM.