use strict;
use warnings;
use SOAP::Lite +trace => [
    transport => sub {
        my ($in) = @_;
        return if ref $in ne 'HTTP::Response';
        printf "Response length: %d bytes.\n", bytes::length( $in->content );
      }
];

my $sv = SOAP::Lite->new->service('.../foo.wsdl');
$sv->fooMethod( 'foo', 'bar' );