#!/usr/bin/perl 

use strict;
use warnings;
  
use LWP 5.64;
my $browser = LWP::UserAgent->new;

my $xml= qq[<?xml version="1.0" encoding="utf-8" ?>
.... snip ....
];
  
my $url = 'https://www.envmgr.com/LabelService/EwsLabelService.asmx/Ge
+tPostageLabelXML';

my $response = $browser->post(
  $url,
  Content_Type => 'text/xml',
  Content  => $xml
);

print $response->content;