Which version of Perl are you using?
Try
my $msg = pack("C0C*",0x80,0x10, 0x29)
It shouldn't make a difference, but I seem to remember it did one one of the early 5.8.x versions of perl.
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.