How to Find the Size of a Hash Reference in Perl

use strict;

use warnings;

# --- 1. Getting the size of a standard Hash ---

my %hash = (

    'apple'  => 1,

    'banana' => 2,

    'cherry' => 3

);

# The keys() function returns the number of elements when used in a scalar context.

# The string concatenation operator (.) automatically provides this scalar context.

print "Size of standard hash: " . keys(%hash) . "\n";

# --- 2. Getting the size of a Hash Reference ---

my $hash_ref = {

    'foo' => 'bar',

    'baz' => 'qux'

};

my $i = 0;

# Method A: Explicit scalar context using the 'scalar' keyword (often considered more readable)

$i += scalar keys %$hash_ref; 

# Method B: Implicit scalar context (the numeric '+=' operator forces scalar context)

$i += keys %$hash_ref;        

print "Size of hash reference (counted twice): $i\n";