Without knowing all the details, I'd say your best bet would be to validate the user input via JavaScript. Since JavaScript is client-side, you won't need to send the user input to the server and then back again if it's incorrect.

As for outputting the results of your calculations, etc., you can do this the simple way with CGI, or the slightly more complicated way, although with more control and cleaner code, with HTML::Template.

This kind of stuff is very common. Search this site and Google for more information.

UPDATE: As some other monks have caught a mistake in my original post, I should add that I neglected to mention that user input should ALSO be checked at the server-side. However, contrary to what tachyon says, I do believe that JavaScript provides additional security and does have some degree of reliability.

UPDATE Part II: For a good example of using JavaScript to help validate input, check out http://developer.apple.com/internet/webcontent/validation.html.

In reply to Re: How do I write a CGI script with form validation? by rhythmicus
in thread How do I write a CGI script with form validation? by blazesixty

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.