use XML::Rules;
my $parser=new XML::Rules(rules=>{});
...
$XMLContent .= $parser->toXML(packet_ref => {packID => [$foo], packInfo => [$bar]}) . "\n";

# or, with formatting

# $XMLContent .= $parser->toXML(packet_ref => {packID => [$foo], packInfo => [$bar]}, 0, '  ') . "\n";