You should be able to do:

my $shell = $ENV{SHELL} || '/bin/sh';  # or maybe get user's shell fro
+m /etc/passwd
my $home = whatever ...
my $envstr = qx($shell -c '. $home/.profile; env');
# some error checking should go on here

my %NEWENV = map { split /=/, $_, 2 } split /\n/,  $envstr;
[download]

or something like that.