var f = [[], DATA.lines.map {['', .chars..., '']}..., []];

10.times {
    say f.map { .join(" ") + "\n" }.join;
    var a = [[]];
    for y in (1 .. f.end-1) {
        var r = f[y];
        var rr = [''];
        for x in (1 .. r.end-1) {
            var c = r[x];
            rr << (
              given(c) {
                when('H') { 't' }
                when('t') { '.' }
                when('.') { <. H>[f.ft(y-1, y+1).map{.ft(x-1, x+1)...}.count('H') ~~ [1,2]] }
                default   { c }
              }
            )
        }
        rr << '';
        a << rr;
    }
    f = [a..., []];
}

__DATA__
tH.........
.   .
   ...
.   .
Ht.. ......