use File::Finder;
my %sizes;
my @START = ".";
$sizes{$_->[0]} += $_->[1] for
  File::Finder->type('f')->mtime('-3')->collect(sub { [(stat)[4, 7]] }, @START);

for (sort { $sizes{$b} <=> $sizes{$a} } keys %sizes) {
  printf "%20s %.2f MB\n", getpwuid($_) || "($_)", $sizes{$_}/1e6;
}