you are not going to be able to sort this by the fifth field.

[jidanni]

Try as you might, there is no way you are going to sort by this field,
$ LC_CTYPE=zh_TW.UTF-8 w3m -dump \
  
http://www.tcb-bank.com.tw/tcb/servicesloc/atm_location/taichung_county_atm.htm 
|
  perl -anlwe 'print $F[4] if exists $F[4]'|LC_CTYPE=C sort
without ripping it out of the table first using perl. Go ahead, try -t ... -k 
...,...
You won't be able to order that field in the same way one can after
ripping it out of the table.
sort (GNU coreutils) 8.4
P.S., perhaps add a --debug-fields mode which adds field boundary | pipe
symbols into the output.