I do have the exact same problem, and unfortunatly it is not a warning but an error (from apache2 error log):

Cgi scripts are running well otherwise.
Any possible solution or hint?

it is not a warning but an error (from apache2 error log):

No sir, it is a warning. splain

Use of uninitialized value $ENV{"HTTP_TRANSFER_ENCODING"} in pattern m
+atch
        (m//) at /usr/local/share/perl/5.10.0/SOAP/Transport/HTTP.pm l
+ine 530 (#1)
    (W uninitialized) An undefined value was used as if it were alread
+y
    defined.  It was interpreted as a "" or a 0, but maybe it was a mi
+stake.
    To suppress this warning assign a defined value to your variables.

    To help you figure out what was undefined, perl will try to tell y
+ou the
    name of the variable (if any) that was undefined. In some cases it
+ cannot
    do this, so it also tells you what operation you used the undefine
+d value
    in.  Note, however, that perl optimizes your program and the opera
+tion
    displayed in the warning may not necessarily appear literally in y
+our
    program.  For example, "that $foo" is usually optimized into "that
+ "
    . $foo, and the warning will refer to the concatenation (.) operat
+or,
    even though there is no . in your program.
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The part of that says "error" is just boilerplate generated by apache mod_log.

Hello and thank you for your answer!

If it is simply a warning, it shouldn't affect the program behavior and the code should execute itself correctly, isn't it?

When I call the client perl program, the server add the previous error/warning line in the error log and it seems that nothing is returned to the client (it should return "hello, world".)

I don't know what to do now to try to solve this problem :/