>> $a = [1,2,3]
Array(3) [ 1, 2, 3 ]

>> $a[0]      // Perl: $a->[0] 
1

>> $b = $a
Array(3) [ 1, 2, 3 ]

>> $b[0]=666  // Perl $b->[0] = 666
666

>> $a
Array(3) [ 666, 2, 3 ]