#####use strict;
use warnings;
use 5.010;

sub greet {
    my $greeting = shift;
    say $greeting;
}

%greet = (
    a => 'hello',
    b => 'goodbye',
);


my $code_ref = \&greet;
$code_ref->('hello');

my $hash_ref = \%greet;
say $hash_ref->{b};

*greet->('goodbye');
say *greet->{a};


--output:--
hello
goodbye
goodbye
hello