echo(fn());
echo(fn(r=1,d=2));
echo(fn(r="hello"));
echo(fn(r=1,r=2));
echo(fn(r=1, q=5));


WARNING: fn(): expected one of "r" or "d" in file ., line 1
ECHO: undef
WARNING: fn(): specified both "r" and "d" in file ., line 2
ECHO: undef
WARNING: fn(..., r="hello") Invalid type: expected number, found string in file ., line 3
ECHO: undef
WARNING: argument "r" supplied more than once in file ., line 4
ECHO: 8
WARNING: variable "q" not specified as parameter in file ., line 5
ECHO: 8