Make it %local or go loco

Just spent an hour debugging a SAS macro called inside of an outer macro loop and both where using the same macro variable. You should always define macro variables as local within a macro definition. Failure to do so can result in percieved erratic behavior when the outer macro variable value is inadvertantly changed by the inner macro.

Macro parameters are always local by default, but you need to use the %local statement to protect your code. Lesson learned

%macro mymacro( myparam ) ;
  %local myvar ;
%mend ;

Reference: http://support.sas.com/documentation/cdl/en/mcrolref/61885/HTML/default/viewer.htm#a000206835.htm