In addition to the above scripts, try this one:

#! /usr/bin/perl
use Data::Dumper;
$Data::Dumper::Indent = 1;

print "Content-Type: text/plain\n\n";
print Data::Dumper->Dump([\%ENV], ['*ENV']);
[download]

It isn't much of an improvement this time (though it will help in the unusual occurance that any environment variables have data in them special to HTML), but it is handy to know about the options that Data::Dumper has for more complex data structures...