In SAS 9.1, the macro IN operator is a new binary comparison operator
similar to the IN operator used in the DATA step. The character # is an
alternate operator that can be used in the place of the mnemonic IN.
Because of this, the # now has special meaning, and it must be masked
with one of the macro quoting functions in order for it to be seen as
text. If the # is not masked when comparing values on a %IF, the
following error message will be issued:

   ERROR: Operand missing for # operator in argument to %EVAL function.

This can be corrected by using the %QUOTE quoting function.

   %macro test;
     %let x = #ABC#;
     %if %quote(&x) = ABC %then %put Match;
     %else %put No Match;
   %mend test;
   %test

The hotfix referenced at the bottom of this note removes the special
meaning of the #.

After applying this hotfix, the macro IN operator will not be available.
Also, the IN operator will not be available in SAS 9.1.2 and 9.1.3, but
will return in SAS 9.2 where it can be disabled with a system option.

A Technical Support hot fix for SAS 9.1 (TS1M0) for this issue is
available at the following web location.

http://www.sas.com/techsup/download/hotfix/b9_sbcs_prod_list.html#011945

Operating System and Release Information

A fix for SAS 9.1 (9.1 TS1M0) for this issue is available at: