Tokens in the Assuan protocol are generally case-insensitive. The GETATTR token
in scd is not, though:
scd GETATTR SERIALNO
S SERIALNO 89490173300008094100
OK
scd getattr serialno
ERR 100663384 Invalid name <SCD>
scd GETATTR serialno
ERR 100663384 Invalid name <SCD>
scd getattr SERIALNO
S SERIALNO 89490173300008094100
OK