define(`showN',
   `ifelse($1,0,`',`$2
$0(decr($1),shift(shift($@)))')')dnl
define(`showargs',`showN($#,$@)')dnl
dnl
showargs(a,b,c)
dnl
define(`x',`1,2')
define(`y',`,3,4,5')
showargs(x`'y)