You can pass the username and password as parameters in your request, like

my $result = SOAP::Lite
    -> uri('http://www.example.com/Protected')
    -> proxy('http://www.example.com/soap.cgi')
    -> fetchdata($name, $pass, @request)
    -> result;
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And define the fetchdata method at server-side as smth like this (i didn't add SOAP-specific code, but it can be taken directly from SOAP::Lite docs):

package Protected;
sub fetchdata {
    my $pkg = shift;
    my $name = shift;
    my $pass = shift;
    #check the $name and $pass and process @request
    # or send an response indicating authentication error
}
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I have no experience in Java, but as i can see, the code sample you showed seems to do the same thing, but sends only name and password.