You don't need to have your script "remember" all the lines in the current section (which I take it is the issue you want to solve), as long as you are judicious in your use of filehandles. My initial thought is along the following lines:

my $outfilename = "outfilename";

open INFILE, "$input_file" 
    or die "Can't open $input_file: $!\n";

while (<INFILE>) {
    if ( /section-end-marker/ ) {
       close OUTFILE;
       next;
    }
    if ( /section-start-marker/ ) {
        # generate the new $outfilename however
        open OUTFILE, "> $outfilename" or die"$!\n";
        next;
   }
    print OUTFILE;
}
[download]

That's very basic, but the idea is that you print to the currently open filehandle, unless you've found the start section marker, in which case you open the output file (to that filehandle), or the end section marker, in which case you close the curently open filehandle.

HTH

update OK, two people have failed to notice that the code is not to be used "as is": it is a skeleton upon which to build a functioning script. I left this implicit by putting comments where there would, in an actual script, be functioning code. I now make that implict warning explicit.

If not P, what? Q maybe?
"Sidney Morgenbesser"