use strict; use warnings; use feature 'say';

use Path::Iterator::Rule;
use Path::Tiny;

my $root = './1204707';
my $in   = $root . '/A'; 
my $to   = $root . '/B';

my $rule = Path::Iterator::Rule->new;
$rule->file->name( qr/txt$/ );
$rule->file->empty;

my $next = $rule->iter( $in, {
    depthfirst => 1,
    visitor => sub {
        my $path = path( shift );
        my $parent = $path->parent;
        $path->move( $to . '/' . $path->basename );
        rmdir $parent if not $parent->children;
    },
});

while ( defined( my $file = $next->() ) ) {
    say "processing $file";
}

__END__