Thanks much, all! I've used your suggestions to make the code to be shorter, more portable, and more robust:

#!/usr/bin/perl

use warnings;
use strict;

use Getopt::Long;
use URI::Escape;

{
   my %pars = DoGetOptions () if scalar @ARGV;
   my $str = "$pars{browser} $pars{site}" . uri_escape ( join '+', @AR
+GV );
   die "$str\n" if $pars{norun};
   system $str;
}

sub DoGetOptions {
   my @sitelist = qw{ http://www.google.com/search?q=
                      http://dictionary.reference.com/search?q=
                      http://www.ask.com/main/askjeeves.asp?ask=
                      http://thesaurus.reference.com/search?q=        
+                             }; 
    my %pars = (
       picksite => 0,
       site     => '',
       browser  => 'lynx -cookies A',
                   #netcape
                   #firefox
       norun    => 0,
   );

   GetOptions (
       \%pars,
       qw{
           picksite=s
           site=s
           browser=s
           norun
       }
   ) or die "bad options $!";
   $pars{site} = $sitelist[$pars{picksite}] if '' eq $pars{site};

   return %pars;
}
[download]