sublis for not bind(?) variables



I woud like to subt many variables to given exp.
To do this, I try

fexp:x^2+y^2+x*y
/*wrong*/
subtest(x0,y0):=sublis(makelist(var=concat(var,0),var,[x,y]),fexp)
subtest(1,2)
/*wrong result   x0^2  + x0 y0 + y0^2?*/

This does not work.
But simple use of sublis works.

/*work*/
subtest1(x0,y0):=sublis([x=x0,y=y0],fexp)
subtest1(1,2) /* = 7*/
subtest1(10,2) /* =124*/

Are there any method subst to many variables by using loop like
function (mekelist and so on)?