Bailador:

get '/env' => sub {
   my @list = map { $_ ~ ":" ~ request.env<$_> }, request.env.keys;
   @list.join("<br>");
}

Result:
....
use of uninitialized value %!env of type Any in string context  in sub  at app.pl6:20

use of uninitialized value %!env of type Any in string context  in sub  at app.pl6:20

use of uninitialized value %!env of type Any in string context  in sub  at app.pl6:20
...

--------------------------------------

    request.env.pairs.join(" ");

Result:

Cannot use a Buf as a string, but you called the Stringy method on it