in reply to system commands/shell and perl variables.

You may be interested in Xen::API. (I have no experience with this - just found it on CPAN.) 
use Xen::API;
my $x = Xen::API->new;
 
my %vms = $x->list_vms

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                As a computer, I find your faith in technology amusing.

In Section Seekers of Perl Wisdom