Quote

A (file)glob evaluates its (embedded) argument only when it is starting a new list. All values must be read before it will start over. In list context, this isn't important because you automatically get them all anyway. However, in scalar context the operator returns the next value each time it's called, or undef when the list has run out. As with filehandle reads, an automatic defined is generated when the glob occurs in the test part of a while , 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.