my %h = map { chomp; (split /\s+/, $_, 2)[0,1] } <DATA>;
print Dumper \%h;
__DATA__
two 2
one
three 3 X

##</code><code>##

$VAR1 = { 
          'three' => '3 X',
          'one' => undef,
          'two' => '2'
        };

##</code><code>##

my %h = map { defined ? $_ : $default }
        map { chomp; (split /\s+/, $_, 2)[0,1] } <DATA>;