To do a regexp search for "foo" and "bar", in any order, any distance from each other, one would use ^(?=.*foo)(?=.*bar). In the following snippet, a regexp of that form is constructed dynamically:

my $text = 'Perl is a general-purpose programming language originally 
+developed for text manipulation and now used for a wide range of task
+s including system administration, web development, network programmi
+ng, GUI development, and more.';
# Text source: perlintro [http://perldoc.perl.org/perlintro.html]

foreach my $keywords (
   'Perl development',
   'Perl sucks',
) {
   $re = '^' .
         join '',
         map { "(?=.*\\b$_\\b)" }
         map quotemeta,
         split ' ',
         $keywords;

   print("$re\n");

   print("$keywords: ", $text =~ /$re/ ? "match" : "no match", "\n");
}
[download]

^(?=.*\bPerl\b)(?=.*\bdevelopment\b)
Perl development: match
^(?=.*\bPerl\b)(?=.*\bsucks\b)
Perl sucks: no match
[download]

Note: The use of \b is questionable. What if the keywords start or end with characters that don't match \w? This issue is left unresolved.

By the way, you should use core module CGI instead of handling the CGI request in your code. It's much more reliable and maintainable. You should also search if a module already does what I just coded.