XML::LibXML : To extract child and granchildren of a xml tag in perl

Xml Data:

<libraries>
 <group name="stdcell_globalsubtypes">
   <cell type="a" optional="1">
    <cell type="b" optional="1">
      <cell type="c" optional="1" >
        <cell type="d" optional="1" >
         <cell type="e" optional="1"/>
       </cell>
     </cell>
   </cell>
 </cell>
</group>

How can I access all the children and grandchildren nodes of group name = "stdcell_globalsubtypes" without having to parse through each child node using getChildrenByTagName("cell").

I need to parse this xml data and make a hash out of it as %hash = ('1'=>a,'2'=>b,'3'=>c,'4'=>d,'5'=>e)

Is there any API to get all the child nodes and sub child nodes? If not, How can I do it recursively?

Thanks in advance :)

I'm not XML expert... There's probably a more efficient way to solve this, but one way to do it is with a recursive function

use strict;
use warnings 'FATAL', 'all';
use XML::LibXML;

sub extract_cell_types {
    my $node = shift;
    my @return_array;
    my @cells = $node->getChildrenByTagName("cell");
    for my $cell (@cells) {
        my $type = $cell->getAttribute("type");
        push @return_array, $type;
        if ($cell->hasChildNodes) {
            push @return_array, extract_cell_types($cell);
        }
    }
    return @return_array;
}

my $doc = XML::LibXML->load_xml(string => <<'END');
<doc>
<group name="stdcell_globalsubtypes">
 <cell type="a" optional="1">
  <cell type="b" optional="1">
   <cell type="c" optional="1" >
    <cell type="d" optional="1" >
     <cell type="e" optional="1"/>
    </cell>
   </cell>
  </cell>
 </cell>
</group>
</doc>
END

my $doce = $doc->getDocumentElement;

my @types;
my @groups = $doce->getChildrenByTagName("group");
for my $gn (@groups) {
    if ($gn->getAttribute("name") eq "stdcell_globalsubtypes") {
        push @types, extract_cell_types($gn);
    }
}

print join(', ', @types) . "\n";