How about something like this? 
unless ($form{'searchstring'}) {
    $form{'searchstring'}= '[a-zA-Z]';
}
if ($desc =~ /$form{'searchstring'}/i) {
...
}

[download]

It's unclear from your code, but I assume you know that this has to be done in the post-processing of the form, and not at the same time you are asking the form....

Added:
You could always do something like this when you are asking the form: <input type="text" name="searchstring" size="18" VALUE="any character"> Of course, "any character" will appear in the search box every time, and the program will default to searching for "any character" unless you add something like this: 
 
if ($form{'searchstring'} eq "any character") {
    $form{'searchstring'}= '[a-zA-Z]';
}

[download]

In reply to Re: Giving text box a hidden value by fpi
in thread Giving text box a hidden value by SysAdm

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.