Rewrite to use while instead of foreach. I can't tell if this sample is meaningful or not, but may give you the idea (note local data is a good technique for sample code like this):

use strict;
use warnings;

my %DB;
my $store = "<Head>";
my $head;

while (<DATA>) {
    if (/.*<B>/ && ! /Last modified/){ #If line is a title
        my $temp = $_;
        $_=~ s/(<[^<>]+>)+//g; chomp;
        if (/\(/){
            $store = $_;
            $DB{$store} = $temp;
        }else{
            $store = $_;
            $DB{$store} = $temp;
        }
    }else{                              #Not a title
    ($store ne "<Head>")? $DB{$store}:$head .= $_;
    }
}

print join "\n", map {"$_ -> $DB{$_}"} keys %DB;

__DATA__
Title line<B>
a line
another line
<Head><B>
this line
that line

[download]

Prints:

use strict;
use warnings;

my %DB;
my $store = "<Head>";
my $head;

while (<DATA>) {
    if (/.*<B>/ && ! /Last modified/){ #If line is a title
        my $temp = $_;
        $_=~ s/(<[^<>]+>)+//g; chomp;
        if (/\(/){
            $store = $_;
            $DB{$store} = $temp;
        }else{
            $store = $_;
            $DB{$store} = $temp;
        }
    }else{                              #Not a title
    ($store ne "<Head>")? $DB{$store}:$head .= $_;
    }
}

print join "\n", map {"$_ -> $DB{$_}"} keys %DB;

__DATA__
Title line<B>
a line
another line
<Head><B>
this line
that line

[download]
DWIM is Perl's answer to Gödel

In reply to Re: Reading from large files by GrandFather
in thread Reading from large files by zer

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.