difference between && and 'and'

a.pl

use common::sense; 

sub a { say "a"; 2 }
sub b { say "b"; 0 }
sub c { say "c"; 1 }
sub ok { say "ok"; 3; }
sub nok { say "nok"; 4; }

my $x = a and b and c and ok or nok;

my $y = a && b && c && ok || nok;

say "x=$x, y=$y";

__DATA__
output:

a
b
nok
a
b
nok
x=2, y=4