In list context, returns a (possibly empty) list of filename expansions on the value of EXPR such as the standard Unix shell /bin/csh would do. In scalar context, glob iterates through such filename expansions, returning undef when the list is exhausted. This is the internal function implementing the <*.c> operator, but you can use it directly. If EXPR is omitted, $_ is used. The <*.c> operator is discussed in more detail in "I/O Operators" in perlop.
Beginning with v5.6.0, this operator is implemented using the standard File::Glob extension. See File::Glob for details.