First my code 

  $search = $top->Entry ('-width' => 20,
                           ) ->pack('-side' => 'left');

    $search->bind('<KeyPress-Return>', \&search);



sub search
   {
   SEARCH_GET:

     my ($search_pattern , $string   );
      $search_pattern = $search->get();

     print "Pattern entered into Search-box is:  $search_pattern\n   "
+;

      (goto SEARCH_GET) if (! (defined $search_pattern)  ); # if <RET>
+ is entered by itself, then ignore it...

      if ( $search_pattern =~ /^([\w\s\-\:\_\d]+)$/   )  ## CHECK $sea
+rch_pattern and untaint:
    {                                              ## make sure it onl
+y contains \w, '-' , ':' , '_' , and digits
          $string = $1;                                ## DON'T forget
+ 's -- space between prog and $arg

      print "\$string is untainted; \$string = $string \n ";
    }
        else
           {
             print "OOPS! data is tainted. TRY AGAIN...\n  ";

           }



                          .
                          .
                          .

   }

[download]

If the first char I enter into the search-box is <RET>, then the program freezes. BESIDES. What was entered? Was it \n or " " or undef? How do I catch a carriage-return that was entered by itself , and thus prevent the programs freezup?

In reply to Stopping bad input (harder than sanitizing) by Anonymous Monk

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.