Basically, the code in Get default login environment respectively its replies should allow you to read all the environment variables a shell script sets.

You will need to learn about how your shell (cmd.exe) invokes batch files and how you can run your own code in the context of such a batch file, but it's not hard. The following code works for me to retrieve the environment for a batch file under Windows:

my $batchfile= 'C:\\test.cmd';
my $cmd= qq("$batchfile" && set);
print "Environment: $_"
    for `$cmd`;
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... where test.cmd contains

set TEST=C:\test.pl
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You should easily be able to combine this part with the parsing parts of Get default login environment into something that retrieves the environment under Windows.