Automatically call hash values that are subroutine

Question

I have a hash with a few values that are not scalar data but rather anonymous subroutines that return scalar data. I want to make this completely transparent to the part of the code that looks up values in the hash, so that it doesn't have to be aware that some of the hash values may be anonymous subroutines that return scalar data rather than just plain old scalar data.

To that effect, is there any way to have the anonymous subroutines executed when their keys are accessed, without using any special syntax? Here's a simplified example that illustrates the goal and the problem:

#!/usr/bin/perl

my %hash = (
    key1 => "value1",
    key2 => sub {
        return "value2"; # In the real code, this value can differ
    },
);

foreach my $key (sort keys %hash) {
    print $hash{$key} . "\n";
}

The output I would like is:

perl ./test.pl
value1
value2

Instead, this is what I get:

perl ./test.pl
value1
CODE(0x7fb30282cfe0)

Answer 1

No, not without some ancillary code. You are asking for a simple scalar value and a code reference to behave in the same way. The code that would do that is far from simple and also injects complexity between your hash and its use. You might find the following approach simpler and cleaner.

You can make all values code references, making the hash a dispatch table, for uniform invocation

my %hash = (
    key1 => sub { return "value1" },
    key2 => sub {
        # carry on some processing ...
        return "value2"; # In the real code, this value can differ
    },
);

print $hash{$_}->() . "\n" for sort keys %hash;

But of course there is a minimal overhead to this approach.