Because XML will produce a nested structure of arrays and hashes at arbitrary depth, you'll anyway need to test what is found recursively. e.g.:

# load XML into $tree here, then ...
traverse ($tree);

sub traverse {
    my $tree = shift;
    if (ref($tree) eq 'ARRAY') {
        traverse($_) for (@$tree);
    }
    elsif (ref($tree) eq 'HASH' ) {
        while (my ($k, $v) = each %$tree) {
            # process key $k
            traverse($v);
        }
    }
    elsif (!ref($tree)) {
        # process $tree as a scalar here
    }
    else {
        die "unexpected type of reference: " . ref($tree);
    }
}
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