use List::Util 'reduce';

sub hash_char_count :prototype(\%) {
    my $href = shift;
    return reduce {$a += length $b} 0, %$href;
}

my %hash = (foo => 'bar', baz => 1, fiddle => 'faddle');

print hash_char_count(%hash), "\n";

##</code><code>##

# ... 

sub hash_char_count {
    # ...
}

# ...

print hash_char_count(\%hash), "\n";