Hyperlinked call numbers (different than before)

OK, below is the relevant section of code:

function theme_biblio_long($node,$base='biblio',$style='classic') {

/*
*
* <snip>
*
*/

  if ($node->biblio_call_number) {
	$cubb = substr($node->biblio_call_number,0,4);
	if ($cubb == "Cubb") {	//case for Cubberley books
		$cubbref = substr($node->biblio_call_number,0,8);
		if ($cubbref == "Cubb Ref") {	//case for Cubberley Reference books
			$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/reference?size=_original") . "\n";
		} else { //case for Cubberley non-reference books
			$callnumber = substr($node->biblio_call_number,5,3);
			if(is_numeric($callnumber)) { //Case for Deweys
				if ($callnumber >= 372) {
					$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/north_balcony?size=_original") . "\n";
				} else {
					$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/south_balcony?size=_original") . "\n";
				}	
			} else { //Case for LOCs
				$lb = 'LB';
				$lb_split = '1028.5';
				$callnumber = substr($node->biblio_call_number,5,10);
				preg_match_all('/[A-Z]{1,2}|[0-9]{1,4}\.[0-9]{1,3}|[0-9]{1,4}/',$callnumber,$callnumber_array);
/* this ^^^ looks in $callnumber for numeric up to 2 characters (section), numeric up to XXXX.XXX (number w/ decimal), 
*  then numeric up to 4 digits (number non-decimal)
*  then puts all that stuff into $callnumber_array
*/
				$lb_evaluate = strcmp($lb,$callnumber_array[0][0]);
				switch ($lb_evaluate) {//three-case scenario: <LB, >LB, =LB
					case 0:
						if (is_numeric($callnumber_array[0][1])) {
							if ($callnumber_array[0][1] >= $lb_split) { //case for > LB1028.5
								$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/south_stacks?size=_original") . "\n";
							} else { //case for <LB1028.5
								$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/north_stacks?size=_original") . "\n";
							}
						} else {
 					$output .= '<h3>'.t("Call Number").':</h3> ' . check_plain($node->biblio_call_number) . "\n" . $cubb;  //makes non-hyperlinked if the preg_match_all function did not return a numeric value
						}
						break;
					case 1:
						$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/north_stacks?size=_original") . "\n";
						break;
					case -1:
						$output .= '<h3>'.t("Call Number").':</h3> ' . l(check_plain($node->biblio_call_number),"stacks/south_stacks?size=_original") . "\n";
						break;
				}
			}
		}
	} else {
		$output .= '<h3>'.t("Call Number").':</h3> ' . check_plain($node->biblio_call_number) . "\n";  //makes non-Cubberley books non-hyperlinked
	}
  } //end all call number processing

  if ($node->biblio_accession_number) $output .= '<h3>'.t("Accession Number").':</h3> ' . check_plain($node->biblio_accession_number) . "\n";

/*
*
* <snip>
*
*/

  return $output;
}

One of the risks of pursuing this would be that of feature bloat. Biblio does what it does well, and trying to turn it into something it's not (e.g., an OPAC) may be barking up the wrong tree. Thanks for giving it some consideration. It's working for me based on the above modifications, so unless there's a general clamor for it, it probably wouldn't be worth the effort.

Thanks for the tip on the l() function. I'm a PHP hack; I typically can do just enough to get something working, so it's good to have knowledgeable input.