Misleading error message from exec_com processor

[David Rosenberg]

The following exec_com contains an error.

&version 2
&if &[or true &[equal A B] &then &print Misleading error message

The letter B should be followed by two close square brackets, not just one. However, the error message produced is
Nested control statement keyword "&then"
which seems to be rather misleading since there is only one occurrence of "&then" and hence it can't be nested.

[David Rosenberg]

In other situations, missing or extra close brackets are diagnosed correctly.

The command

enter_abs_request set_timezone -time ||"11/05/23  0200.0 edt Sun"]

produced the correct, helpful error message
command_processor_: Brackets do not balance.

and

&set arg_num 0
&set arg_num &[plus &(arg_num) 1]]

also produced the same correct, helpful error message
command_processor_: Brackets do not balance.