Can I just say how marvellous it is to see someone with use English; and then going on to use single letter variable names?

But for the sake of being more helpful - to match the _content_ of an element, you probably want the "string()" function in your XPath:

use strict;
use warnings;

use English;
use XML::Twig;

my $xmlFile = "demo.xml";

my $t = XML::Twig->new(
        pretty_print => 'indented_a',
        keep_atts_order => 1,  
        twig_handlers => { 
           q(myconfig/myobj[string(uniqueName)=" objA "]/myattributes/
+attribB) => \&getfoo,
        }   
);
$t->parse ( \*DATA );

$t->print;

exit 0;

sub getfoo {
    my ($t, $e) = @_; 
    print "text=", $e->text(), 
          "' tag='", $e->tag(), 
          "' path='", $e->path(), 
          "' parentTag='", $e->parent->tag(), "'\n";
}

__DATA__
<myconfig>
    <myobj>
        <uniqueName> objA </uniqueName>
        <myattributes>
            <attribA> fooA </attribA>
            <attribB> fooB </attribB>
        </myattributes>
    </myobj>
    <myobj>
        <uniqueName> objB </uniqueName>
        <myattributes>
            <attribA> fooA </attribA>
            <attribB> fooB </attribB>
        </myattributes>
    </myobj>
</myconfig>
[download]

Although actually I'd probably be suggesting not using twig_handlers or roots unless you've a need to keep memory footprint down, and just use "get_xpath" and "children" etc. to process it after parsing

foreach my $elt ( $t -> get_xpath( '//myconfig/myobj/uniqueName[string
+()=" objA "]/../myattributes/attribB' ) ) {
   $elt -> print;
}
[download]

Or just iterate all the "myobjs" and extract differentiating elements.