Resolving macro containing %eval in macro variable name, SAS - variables

Question

this is a toy example in order to help with a larger problem I have. It essentially involves using a %eval() macro when referencing a bigger macro variable name.
I have created a macro variable x_2, which uses the values of the loop, '&it', the variable is created successfully as can be seen by the final output, however I can only put it to the log without evaluating &it+1, which I will need to do when using a loop bigger than size 1.
It seems to resolve x_ first, giving a warning, before then evaluating x_2 as a whole and giving the output.
I realise this is just a problem about how to reference macros correctly, but I cannot find any examples where it uses an evaluation as part of a macro variable name.
Thanks.
%macro testing;
%DO it = 1 %TO 1;
data dataset;
s=100;
t=99;
run;
data _null_;
set dataset;
if s = 100 then do;
call symput("x_%eval(&it+1)",t);
end;
run;
%put "&x_%eval(&it+1)";
%put &x_2;
%END;
%mend testing;
%testing;
LOG OUTPUT
MLOGIC(TESTING): %PUT "&x_%eval(&it+1)"
WARNING: Apparent symbolic reference X_ not resolved.
SYMBOLGEN: Macro variable IT resolves to 1
SYMBOLGEN: Macro variable X_2 resolves to 99
" 99"
MLOGIC(TESTING): %PUT &x_2
SYMBOLGEN: Macro variable X_2 resolves to 99
99
MLOGIC(TESTING): %DO loop index variable IT is now 2; loop will not iterate again.
MLOGIC(TESTING): Ending execution.

Answer 1

Indeed, SAS does the variable substitution before calling the %eval function
The easiest solution is to call %eval in an earlier statement
%let xNr = %eval(&it+1);
%put "&&x_&xNr";
The double ampersand serves to delay the evaluation of x_&xNruntil &xNr is evaluated to 2 and not have the warning that x_ is undefined.
SYMBOLGEN: Macro variable IT resolves to 1
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable XNR resolves to 2
SYMBOLGEN: Macro variable X_2 resolves to 99
" 99"

Answer 2

Agree with Dirk's answer. But as a thought exercise, it is possible to achieve the desired result with ugly use of quoting functions:
%let x_2=99;
%let it=1;
%put %unquote(%nrstr(&x_)%eval(&it+1));
So %nrstr hides the & until after the %eval has done its work (I think. :)
Update:
#Shenglin added a similar answer in a comment that I like better than my approach above:
%put %superq(x_%eval(&it+1));
This works because %superq() is unusual in taking a macro variable name as a parameter (no leading &), not a macro variable reference. So you can use %EVAL to generate part of the name of the macro variable. You could %unquote() if wanted, but it should not be necesssary.

Answer 3

It is much easier to build the macro variable name into another variable and then expand the value.
%let t2=found;
%let mvar=t%eval(1+1);
%put &&&mvar;

Answer 4

Could you try "&&x_%eval(&it+1)"?