$ perle 'use constant X => (1,3); my @y = "a".."z"; say for @y[X]'
Scalar value @y[X] better written as $y[X] at -e line 1.
b
d
$ perle 'use constant X => (1,3); my @y = "a".."z"; say for @y[+X]'
Scalar value @y[+X] better written as $y[+X] at -e line 1.
b
d
$ perle 'use constant X => (1,3); my @y = "a".."z"; say for @y[X()]'
b
d