formattedRead: The number of variables filled. If the input range r ends early,
this number will be less than the number of variables provided. Example: ---- // test.d void main() { import std.stdio; foreach (_; 0 .. 3) { int a; readf!" %d"(a); writeln(++a); } } ----
% echo "1 2 3" | rdmd test.d
2 3 4