How does this perl one liner in the bash works?

Question

I was looking on how I could sort a file based on the length of each sentence and I came across this snippet from this answer

perl -ne 'push @a, $_ } { print sort { length $a <=> length $b } @a' input
                      ^ ^  

I tested it and it works but I don't have a clue how this works! As far as I can see the syntax is wrong. It has an open right bracket and a non closed right bracket which I have marked.
I am really having trouble figuring out how to run perl commands like this in bash
Could some one please explain this snippet?

Answer 1

}{ is so called butterfly or Eskimo greeting Discovered by Abigail, in 1997.

Basically it closes while loop imposed by -n switch, and what follows }{ is block executed after while loop.

This is how perl parses this line,

perl -MO=Deparse -ne 'push @a, $_ } { print sort { length $a <=> length $b } @a' input

---

LINE: while (defined($_ = <ARGV>)) {
    push @a, $_;
}{ # <==here it is

    print((sort {length $a <=> length $b;} @a));
}

A more common way would be using END{} block instead of }{ operator:

perl -ne '
  push @a, $_ 
  END { 
    print sort { length $a <=> length $b } @a
  }
' input