if ($score > $warnrate) {
      print "OK, rf is $score. \|Mbps=$score\n";
      exit 0
    # $score is necessarily <= $warnrate at this point
    #} elsif (($score <= $warnrate) && ($score > $critrate)) {
    } elsif ($score > $critrate) {
       print "WARNING, rf is $score. \|Mbps=$score\n";
       exit 1
    # $score is necessarily <= $critrate at this point
    #} elsif ($score <= $critrate) {
    } else {
       print "CRITICAL, rf is $score. \|Mbps=$score\n";
       exit 2
    # should never reach this point
    } else {
       print "UNKNOWN, rf is $score and something is wrong.\n";
       exit 3
    }

##</code><code>##

   my $line   = `/usr/bin/snmpwalk -v1 -c public $radio .1.3.6.1.4.1.5454.1.40.2.4.0`;
   my @values = split(' ', $line);
   my $score  = $values[3];
   if ...