use URI qw( );

chomp( my $data = <<'__EOI__' );
<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE MESSAGE SYSTEM "http://127.0.0.1/psms/dtd/message.dtd" ><MESSAGE><USER USERNAME="test" PASSWORD="XXXXXX"/><SMS UDH="0" CODING="1" TEXT="The flight # <101> "DEL" to "BLR" is delayed and it's revised time will be informed later. Have a nice day!" PROPERTY="0" ID="1"><ADDRESS FROM="ValueFirst" TO="91XXXXXXXXXX" SEQ="1" TAG="some clientside random data" /></SMS></MESSAGE>
__EOI__

my $url = URI->new('http://api.url/psms/servlet/psms.Eservice2');
$url->query_form(
    data   => $data,
    action => 'send',
);

print "$url\n";