Thank you very much zwon! Your script work just fine for me. I've made some changes to the code so that I can define what is the input file. But I'm not sure whether this is the correct way of doing it or not. Thank you for showing me how the regex work to match certain text i want. Thank you 
my ($frg) = @ARGV;
$frgfile = "$frg";
open(frgfile) or die("Unable to open FRG file");

while(<frgfile>) {
    if (/^{FRG/../^}/){
        if (/^acc:(\d+)/) {
            print ">$1\n";
        }
        elsif ( /^seq:/ ) {
            while(<frgfile>) {
                last if /^\./;
                print;
            }
        }
    }
}

[download]

In reply to Re^2: Vertical Regex by joomanji
in thread Vertical Regex by joomanji

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.