Adjust to the moving target called the C++ standard. Apparently nowadays it's not allowed to define an explicit copy constructor but not an assignment operator. Consequently, defining the explicit copy constructor in terms of the implicit/automatic assignment operator for general convenience no longer works. Add assignment operators. Caution: not tested with the IBM compiler, but there's no particular reason it shouldn't work.

[
  disregard ws
]

file $
  -> thing, eof

thing
  -> '[', "blah ", ']'
  -> word

word
  -> letter
  -> word, letter

ws
  -> space + tab

letter = 'a-z'
space = ' '
tab = '\t'
eof = '\n'