use strict;
use warnings;
use feature 'say';

# an anonymous sub is a code ref
my $square = sub { $_[0] * $_[0] };
# call it with ->()
say $square->(5);
# \& references a named sub
sub greet { "hi $_[0]" }
my $g = \&greet;
say $g->("ada");

anon subs and \&