my $soap = SOAP::Lite
  ->uri($uri)
  ->proxy($proxy)
  ->deserializer( My::Deserializer->new() );

$soap->DoSomething();

#####
# fake deserializer, for debugging purposes

package My::Deserializer;
use SOAP::Lite;
use base qw(SOAP::Deserializer);

sub deserialize {
    require Data::Dumper;
    warn "deserializer : ",Dumper(@_);
    SOAP::Deserializer::deserialize( @_ );
}