A filehandle is opened but the file operations are performed "in-memory"
on a scalar variable. All the normal file operations can be performed
on the handle. The scalar is considered a stream of bytes. Currently
fileno($fh) returns undef.
IMPLEMENTATION NOTE
PerlIO::scalar
only exists to use XSLoader to load C code that
provides support for treating a scalar as an "in memory" file.
One does not need to explicitly usePerlIO::scalar
.