What is the point of the & / ampersand sigil for function refs?

[tphyahoo]

In the following code, I can call a module function using &, or not using &. Is there ever a scenario when it's preferrable to use the &? Where can I learn more about this?

#!perl
#test.pl
use strict;
use warnings;

#custom modules
use lib 'E:/data/entwicklungsArena/perl/development/modules';
#Works
use Misc::Logger;
print 'without &: ';
Misc::Logger::logMessage("test");
#Also works: 
print 'with &: ';
&Misc::Logger::logMessage("test");