$q{'command'} =~ /^(search|\s*)$/;
$command = $1; # $command is now untainted.

##</code><code>##

defined $command && $command eq 'search' ? &search : &main; # gosh, I love the trinary operator :)

##</code><code>##

while ($firstDisp < $lastDis) {...}

##</code><code>##

use CGI;
my $q = new CGI;

##</code><code>##

$q->param('command') =~ /^(search|\s*)$/; # untaint 'command'
my $command = $1; # $command is now untainted.