#!/usr/bin/env perl
use strict;
use warnings;

use 5.010;

use LWP::UserAgent;
use SOAP::Lite;

my $client = SOAP::Lite->proxy($proxy)
    ->ns($namespace, 'foo')  # I'm not sure I understand this.
    ->uri($uri)
    ->on_action(sub { sprintf '%s', $_[0] })
    ->on_fault(sub {
       my($soap, $result) = @_;
       die ref $result ?
        "Fault Code: " . $result->faultcode . "\n" 
            .  "Fault String: " . $result->faultstring . "\n"
        : $soap->transport->status, "\n";
     });

my $params = { foo => 'bar', biz => 'baz'};

my $result = $client->my_api_method($params);

##</code><code>##

my $data = SOAP::Data->name( %params);
#say "Data: $data";

my $serializer = $client->serializer;
my $xml = $serializer->envelope(method => 'my_api_call', $data);

##</code><code>##

#!/usr/bin/env perl
use strict;
use warnings;

use 5.010;

use LWP::UserAgent;
use SOAP::Lite;

my $client = SOAP::Lite->proxy($proxy)
    ->ns($namespace, 'foo')  # I'm not sure I understand this.
    ->uri($uri)
    ->on_action(sub { sprintf '%s', $_[0] })
    ->on_fault(sub {
       my($soap, $result) = @_;
       die ref $result ?
        "Fault Code: " . $result->faultcode . "\n" 
            .  "Fault String: " . $result->faultstring . "\n"
        : $soap->transport->status, "\n";
     });

my $params = { foo => 'bar', biz => 'baz'};

$client->transport->add_handler("request_prepare", \&modify_header );

my $result = $client->my_api_method($params);

sub modify_header {
    my ($request, $ua, $h) = @_;

    $request->header('some-special-header' => sha1 $request->content);

}