import std.range: chunks;
import std.array: join;
void main() {
    const data = ["a1", "b2", "c3", "d4", "e5"];
    foreach (c; chunks(data, 2))
        string r = join(c);
}


DMD 2.059head gives:

test.d(6): Error: template std.array.join(RoR,R) if (isInputRange!(RoR) && isInputRange!(ElementType!(RoR)) && isForwardRange!(R) && is(Unqual!(ElementType!(ElementType!(RoR))) == Unqual!(ElementType!(R)))) does not match any function template declaration
test.d(6): Error: template std.array.join(RoR,R) if (isInputRange!(RoR) && isInputRange!(ElementType!(RoR)) && isForwardRange!(R) && is(Unqual!(ElementType!(ElementType!(RoR))) == Unqual!(ElementType!(R)))) cannot deduce template function from argument types !()(const(immutable(char)[])[])