my $item = pop @work;
my ($tree, $str) = @$item; #  $data->{a}, einrst
push @work, [$data->{a}{e}, 'inrst'] if $data->{a}{e};
push @work, [$data->{a}{i}, 'nrst'] if $data->{a}{i};
push @work, [$data->{a}{n}, 'rst'] if $data->{a}{n};
push @work, [$data->{a}{r}, 'st'] if $data->{a}{r};
push @work, [$data->{a}{s}, 't'] if $data->{a}{s};
push @work, [$data->{a}{t}, ''] if $data->{a}{t};