It's difficult to know what exactly you mean with such limited information, but I think that you probably want something along these lines: 
use CGI qw(:cgi);
use strict;

my $flatfile = "somefile.txt";
my $query = CGI->new();
my $text = $query->param("text_box");

open(FLATFILE, ">>somefile.txt") or die "Open failed, $!";
print FLATFILE "$text\n\n";
close(FLATFILE);

print "Content-type: text/html\n\n";
print "Success!";

[download]
This code assumes that A. you want to append the data to a growing file with each submission, and B. you only want the data from a single form field called "text_box".

Update: Oh, and it also assumes that you want 2 line breaks between each entry in the text file.

Hot Pastrami

In reply to Re: Storing multi-line form data in a flat file? by Hot Pastrami
in thread Storing multi-line form data in a flat file? by SilverB1rd

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.