Thats somehow a paradox question, cause XML is supposed to be a good textual format, so why don't you parse it on the "server" side?

Anyway if the other side also speaks Perl you could use Data::Dumper to serialize¹ the data (if it's purely textual)

Otherwise JSON and YAML are widespread options.

update

¹) here a snippet from the docs:

use Data::Dumper;
 
#...

$boo = [ 1, [], "abcd", \*foo,
         {1 => 'a', 023 => 'b', 0x45 => 'c'},
         \\"p\q\'r", $foo, $fuz];
 
# ...

$bar = eval(Dumper($boo));
print($@) if $@;
print Dumper($boo), Dumper($bar);
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use $data=Dumper($boo) on sender side and $bar = eval($data) on receiver side.