Testing reveals it only applies when deleting keys (as opposed to values).

use strict;
use warnings;

use Win32::TieRegistry ( Delimiter => '/' );

my $key_path = 'LMachine/Software/DELETE ME/';

$Registry->{$key_path} = {};

$Registry->FastDelete($ARGV[0]);
my $res = delete $Registry->{$key_path};
if( $res )
{
    print( "removed value and res is $res\n" );
}
else
{
    print( " delete failed and res is '$res'\n" );
}
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>perl test.pl 0
removed value and res is HASH(0x225374)

>perl test.pl 1
removed value and res is 1
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