As far as I know, that really depends on the operating
system and how it handles open file handles. However, most
of the time it will buffer the file--read in one line at a
time. I wouldn't worry about it.
Just don't do something like this:
open(FILE, "somefile") or die $!;
my @log = <FILE>; # read entire file into RAM
close(FILE);
foreach my $line (@log) {
# do stuff to $line
}
That will definitely clutter up your machine's memory!
On the other hand, if you have a gigabyte of RAM and
you WANT to load the entire file instead of using slow
disk accesses, knock yourself out. =)