while($line = <DATA>){
	chomp $line;  	($junk,$o_country,$o_province,$o_tcenter,$o_address,$o_city,$o_stprov,$o_mailcountry,$o_postalcode,$o_firstname,$o_lastname,$o_title,$o_phone,$o_fax,$o_date) = split(/\|/,$line);
		#the hashes are filled using the test center as the key
		$testcenters{$o_city} = $o_tcenter;  
		$centercity{$o_tcenter} = $o_city;
		... (more values stored)

@mycenters = sort byString keys %testcenters; #returns list of centercity in alpha order
foreach $city(@mycenters){
    foreach $center($testcenters{$city}){
           print "$testcenters{$city}<BR>";  #print testcenter name
   ... (print more stuff here)
  }
}