CAS Vars and integrals

[robmio]

Hello everyone. I have a problem to raise. I wrote a small #cas-program (see below) which performs a definite integral. Each time I launch the program, the integration variable (for example “t”) is stored in “CAS Vars”. Is there any way to avoid storing the variable in “CAS Vars”?
Also, sometimes not only the integration variable is stored in “CAS Vars”, but other things like question marks or whatever. How do I avoid this.
Best regards, Roberto.

Code:

#cas
Beta_r(z,a,b):=
BEGIN
LOCAL funz;
funz:=(t)→(t^(a-1)*(1-t)^(b-1));
RETURN int(funz(t),t,0,z);
END;
#end
[code]