I was looking at an old StackOverflow question about generating an explicit null XML namespace and had the thought, "maybe an object that stringifies to the empty string, but is true in every other context, will trick LibXML into doing what the seeker of wisdom required."

It did not, nor did an earlier attempt using than Scalar::Util's dualvar. Still I liked my little Empty but True module enough to post it here. (Seems too useless/dangerous/not worth the bother to be on CPAN.)

package MyEmptyTrueVar;
our $singleton;

use overload fallback => 'TRUE',
  '""' => sub { "" }, # Return empty string on stringification
  bool => sub { 1 },  # Return true in boolean context
  '0+' => sub { 1 },  # Return true in numeric context
  cmp  => sub { !ref $_[1] }; # unequal to empty string, or any other 
+string

bless $singleton=\$singleton;
[download]

usage:

say "Single str='$MyEmptyTrueVar::singleton', Num=", (0+$MyEmptyTrueVa
+r::singleton)
   if $MyEmptyTrueVar::singleton &&
   $MyEmptyTrueVar::singleton ne '' &&
   '' ne $MyEmptyTrueVar::singleton;
[download]

shows that Single str='', Num=1.