Looking at the Open Nebula API I see that your requested "one vm list" command maps to the one.vmpool.info XML-RPC method.

Looking at OpenNebula.pm line 128, we see that

my $data = $self->_rpc("one.vm.info", [ int => $id ]);
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so clone that subroutine, and make your own script that fetches the one.vmpool.info instead. Then, with "use Data::Dumper;" try to dump $data and see if there is useful information.

EDIT:

Net::OpenNebula::RPCClient is what you need (untested, but at least it runs without me having OpenNebula):

use Data::Dumper;
use Net::OpenNebula::RPCClient;

my $one = Net::OpenNebula::RPCClient->new(
    url      => "http://server:2633/RPC2",
    user     => "oneadmin",
    password => "onepass",
 );
 
my $ret = $one->_rpc("one.vmpool.info");

die Dumper $ret;
#die Dumper $one;
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OLD, probably BAD STUFF:

 use Data::Dumper;
 use Net::OpenNebula;
 my $one = Net::OpenNebula->new(
    url      => "http://server:2633/RPC2",
    user     => "oneadmin",
    password => "onepass",
 );
my $data = $one->_rpc("one.vmpool.info");
die Dumper \$data;
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sorry for being vague... I do not know the module, nor your application.