The environment is converted into an XML format and then outputted to
a gzipped file (using gzfile). The values in the
environment are serialized (using serialize) in ASCII
format although the keys are stored in plain text.
The format of the XML is very simple, with the primary block being
values, which contain blocks of entries, and each entry
having a key and a value. For instance, if we had an
environment with one value in it, the character c with a key
of a (e.g. assign("a", "c", env=foo)), this is what the
output would look like.