Thanks for the reply! I've taken the time between posting and your response to dive much deeper into XML than I have before. What I think I want can be accomplished with XPath. I believe your solution does something similar.
Here's what I came up with so far. Please chime in on my approach. First, though, I have to clarify that my original XML file example was not 100% representative of my structure. It looks more like this
<a>
<b id='id1' type="1"/>
<b id='id2' type="1.5"/>
<b id='id3' type="2"/>
<c id='id4'/>
<b id='id5' type="3"/>
</a>
Then, I can use XML::XPath to get what I want using the following
use warnings;
use strict;
use XML::XPath;
use XML::XPath::XMLParser;
my $xmlFile = "try.xml";
# create an object to parse the file and field XPath queries
my $xpath = XML::XPath->new(filename => $xmlFile) || die "Problem: $!\
+n";
# look for the preceding sibling node to the one in question
my $nodeset = $xpath->find('//*[@id=' . "'id4']/preceding-sibling::*[1
+]");
foreach my $node ( $nodeset->get_nodelist ) {
print XML::XPath::XMLParser::as_string( $node ) . "\n";
}