This is new since SAS 9.3 on how to display macro variable name and its value. Try to run
%let var=1,2,3;
%put &=var;
or
%macro test(var);
%put &=var;
%mend;
%test(%str(1,2,3))
and you will get in Log window
VAR=1,2,3
You can read from SAS 9.3 online doc:
If you place an equal sign between the ampersand and the macro variable name of a direct macro variable reference, the macro variable’s name displays in the log along with the macro variable’s value.
In SAS 9.2 and prior, you should type the macro variable twice:
%let var=1,2,3;
%put var=&var;
PS: it is called a “Tip” in SAS 9.3 online doc, but I’d rather call it a trick: not critical but nice to have (save your typing!). You may be also interested in Rick Wicklin’s differentiation on Tip and Technique.