First of all, you change $root to $kid1. But I also missed a "@".

#!/usr/bin/perl -w

use strict;

use XML::LibXML;

my $xmlfile = "20060402-201025.xml";

my $parser = XML::LibXML->new;
my $doc    = $parser->parse_file($xmlfile);
my $root   = $doc->getDocumentElement;

my @lats =
    map $_->getValue(),
    $root->findnodes(
        '/datatable/data/datacolumn[@name="Latitude"]/item/@value'
    );

print "$_\n" for @lats;
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