regex error

[Jabba Laci via Digitalmars-d-learn]

I'm working on an Advent of Code problem (2015, Day 5, Part 2), 
and my code doesn't work in D. In Python I get the correct result.

Here is a string:
    const s = "xdwduffwgcptfwad";

The instructions says: "It contains a pair of any two letters 
that appears at least twice in the string without overlapping, 
like xyxy (xy) or aabcdefgaa (aa), but not like aaa (aa, but it 
overlaps)."

Here, "fw" appears twice. My D code:

    auto m1 = matchFirst(s, regex(r"(..).*\1"));

returns an empty m1 object. What am I doing wrong? The same regex 
works in Python.