A string is larger than an integer is larger than undef. Proof:
#! /usr/bin/perl -w
use strict;
use Devel::Size qw(total_size);
my %hash1 = (
shave => '',
the => '',
modern => '',
way => '',
);
my %hash2 = (
shave => 1,
the => 1,
modern => 1,
way => 1,
);
my %hash3 = (
shave => undef,
the => undef,
modern => undef,
way => undef,
);
print "1: " . total_size(\%hash1) . "\n";
print "2: " . total_size(\%hash2) . "\n";
print "3: " . total_size(\%hash3) . "\n";
__END__
1: 309
2: 261
3: 245
If you want the fastest way to initialize that hash, I believe it is
my %hash;
undef(@hash{qw(shave the modern way)});
but your maintenance programmer may have something nasty to say about that.