Perl multiplex test is flaky

BEGIN failed--compilation aborted at /thrift/src/lib/perl/test/multiplex.t line 35.
# Looks like your test exited with 255 before it could output anything.
/thrift/src/lib/perl/test/multiplex.t ...... Dubious, test returned 255 (wstat 65280, 0xff00)
Failed 6/6 subtests