A glob evaluates its (embedded) argument only when it is
       starting a new list.  All values must be read before it
       will start over.  In a list context this isn't important,
       because you automatically get them all anyway.  In scalar
       context, however, the operator returns the next value each
       time it is called, or a undef value if you've just run
       out. As for filehandles an automatic defined is generated
       when the glob occurs in the test part of a while or for -
       because legal glob returns (e.g. a file called 0) would
       otherwise terminate the loop.  Again, undef is returned
       only once.  So if you're expecting a single value from a
       glob, it is much better to say
 
           ($file) = <blurch*>;
 
       than
 
           $file = <blurch*>;
 
       because the latter will alternate between returning a
       filename and returning FALSE.