convert all names of variables in a SAS dataset to lowercase.sas

options mprint; 
%macro lowcase(dsn); 
     %let dsid=%sysfunc(open(&dsn)); 
     %let num=%sysfunc(attrn(&dsid,nvars)); 
     %put #
     data &dsn; 
           set &dsn(rename=( 
        %do i = 1 %to # 
        /*function of varname returns the name of a SAS data set variable*/
        %let var&i=%sysfunc(varname(&dsid,&i));
        &&var&i=%sysfunc(lowcase(&&var&i)) /*rename all variables*/ 
        %end;)); 
        %let close=%sysfunc(close(&dsid)); 
  run; 
%mend lowcase; 

%lowcase(data_with_uppercase_var_names)