Why does this have to be done in a single pass? Reading a file backwards is sufficiently awkward that it pays to use a module such as File::ReadBackwards to handle the ugly work for you. I would probably do it something like this: 

use strict;
use warnings;
use File::ReadBackwards;

open my $forward, '<', 'filename.txt' or die $!;
while( my $line = <$forward> ) {
    last if $line eq "\n";
}
my $blank_position = tell( $forward );
close $forward;
my $bw = File::ReadBackwards->new( 'filename.txt' ) 
    or die "can't read 'filename.txt' $!" ;

while( defined( my $bw_line = $bw->readline ) ) {
    last if $bw->tell() <= $blank_position;
    print $bw_line;
}

[download]

This is untested, but should give you the general framework.


Dave

In reply to Re: read a file in both directions by davido
in thread read a file in both directions by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.