Shell::GetEnv provides facility for obtaining changes made to environment
variables as the result of running shell scripts.  It does this by causing
a shell to invoke a series of user provided shell commands (some of which
might source scripts) and having the shell process store its environment
(using a short Perl script) into a temporary file, which is parsed by the
Shell::Getenv.

Communications with the shell subprocess may be done via standard IPC (via
a pipe), or may be done via the Perl Expect module (necessary if proper
execution of the shell script requires the shell to be attached to a "real"
terminal).