example of "state" keyword in Perl

output.txt

0 on 'a' ~> 1
1 on 'b' ~> 2
2 on 'b' ~> 1
1 on 'b' ~> 2
2 on 'a' ~> 0
0 on 'b' ~> 2
2 on 'a' ~> 0
0 on 'b' ~> 2
2 on 'a' ~> 0
0 on 'b' ~> 2
2 on 'a' ~> 0
0 on 'b' ~> 2
2 on 'a' ~> 0
0 on 'a' ~> 1
1 on 'a' ~> 0

stateful-sub.pl

use strict;
use warnings;
use v5.10;

sub get_next {
    my $char = shift;
    state $current = 0;
    return $current if not $char;
    my $table = {
        0 => {
            'a' => 1,
            'b' => 2,
        },
        1 => {
            'a' => 0,
            'b' => 2,
        },
        2 => {
            'a' => 0,
            'b' => 1,
        }
    };
    $current = $table->{$current}->{$char};
    return $current;
}

my $current_state = get_next;
for my $c ( split //, 'abbbababababaaa' ) {
    print qq{$current_state on '$c' ~> };
    $current_state = get_next($c);
    print qq{$current_state\n};
}