# fastest
my @a = (1);
for (1..10) {
  my $s = @a;
  while ($s-- and my $e = shift @a) {
    push @a, 1, $e;
    $a[-2]++, $s--, shift @a while $a[0] == $e and $s;
  }
}

# shortest
my @a = (1);
for (1..10) {
  my $i;
  @a = map $i++ % 2 : length : $_, join("", @a) =~ /((\d)\2*)/g;
}
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