sub new {
    my $class = shift;
    my $arg = shift; ## What is $arg? Why is it never used?

#    share (my %this); ## this is an obfuscated way to share a variable
    my %this :shared; ## the correct way

    $this{_socket} = shift; ## Presumably this is the socket? Is this where you get the error?
    $this{_sendBufferCount} = 0;

##    bless \%this, $class; ## bless returns the blessed reference; you are throwing it away
##    return \%this; ## this returns an unblessed reference to the hash -- no good for OO.

##  Do it this way.
    return bless \%this, $class;
}