in reply to eval question

I'd like to have an text entry box on a web page to allow users to enter math expresions and calculate them.

Check out this smooth Perl/Ajax/Google Calculator achieved by adding 3 measly lines to a script that Perlmonk varian posted here 2 days ago: 

#!/usr/bin/perl -w

use strict;
use CGI::Ajax;
use CGI qw(:all);
use WWW::Google::Calculator;

my $cgi  = CGI->new;
my $pjx  = CGI::Ajax->new('submitted_formdata' => \&process_formdata);
print $pjx->build_html($cgi,\&show_some_html);

sub show_some_html {
  return <<'END_HTML';
<html>
<head><title>Google Calculator</title></head>
<body><form method="POST">
<b><a
 href=http://www.google.com/help/calculator.html
 title="How to use the Google calculator">Google</a></b>
<input type="text" name="surname" id="surname">
<input type="button" onClick=
 "submitted_formdata( ['surname'],['response1'],'POST');"
   value="Calculate">
</form>
<div id="response1" name="response1"></div>

</body>
</html>
END_HTML
}

sub process_formdata {
  my $surname = shift;
  my $calc = WWW::Google::Calculator->new;
  return $calc->calc($surname) || 'ERROR ' . $calc->error;
}

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