use XML::TreeBuilder;

foreach my $drug ($tree->find_by_tag_name('drug')){

my @targets = $drug->look_down ('_tag', 'targets')->look_down ('_tag', 'target')->attr_get_i('partner');

foreach my $id (@targets){print "\t$id";}

my @actions = $drug->look_down ('_tag', 'targets')->look_down ('_tag', 'known-action')->as_text;

foreach my $act (@actions){print "\t$act";}

}