It might improve things a bit if you rearrange your if statements, you don't need to check ($A + $B == 2...) for each line of the input file, as you know that $B can only change when you've matched RTINSECONDS so you could do this instead :-

    if ($line =~ /TITLE=(.*)/) {
        $title=$1; 
    } 
    elsif
    ($line =~ /RTINSECONDS=(.*)/) { 
        $RT=$1;
        if ($title && grep {$_ eq $TI} @IDS) {
            $IDrtPairs{$TI}=$RT;
            $title = undef;
        }
    }

[download]

As already mentioned it will be better to use a hash, so you should do that too :)

The example input data looks like TITLE & RTINSECONDS are always at the beginning of the line so you could anchor your regexs too, so it can reject non matching lines quicker. i.e. /^TITLE=(.*)/

In reply to Re: Script far too slow with large files - wisdom needed! by RichardK
in thread Script far too slow with large files - wisdom needed! by biologistatsea

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.