Fletch,
If we are going to get silly, why not get ridiculous? 
#!/usr/bin/perl
use strict;
use warnings;

package magic;
sub ENV { defined $ENV{$_[0]} ? $ENV{$_[0]} : 'undefined' };
sub TIEHASH {bless {}, $_[0]} sub STORE {} sub FETCH {ENV($_[1])}

package main;
tie my %magic , 'magic';

print <<"--";
$magic{PATH}
$magic{FOOBAR}
--

[download]

Cheers - L~R

In reply to Re^4: Setting values for undefined environment variables by Limbic~Region
in thread Setting values for undefined environment variables by jacques

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