#first define your headers
 @header = (SOAP::Header->name("FirstHeader")->value("FirstValue"),
    SOAP::Header->name("SecontHeader")->value("SecondValue"));

 #and then do the call. please note the backslash
 my $som=$soap->call( 'method' ,
                   name => 'value' ,
                   name => 'value' ,
                   "soap_headers" => \@header);