my @cityKeys;
my @distanceKeys;

foreach( @cgiParamKeys ) {
  if( /city/ ) {  #If a hidden city field found store it in an array;
    push @cityKeys, $_; #Store the field in an array
    @cityKeys = sort @cityKeys;   #Sort the array
  }
  if( /distance/ ) { #If a hidden distance field found, store it in an array
    push @distanceKeys, $_; #Store it in the array
    @distanceKeys = sort @distanceKeys;  #Sort the array
  }
}