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";
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I like List::Util::reduce for this. It's almost too trivial to bother with a subroutine around it, except that you get to give subroutines descriptive names so people don't have to puzzle over what it's doing.

Sorry for the use of a prototype. Here's without:

# ... 

sub hash_char_count {
    # ...
}

# ...

print hash_char_count(\%hash), "\n";
[download]