Sorry, threads aren't my thing, so I am not the best person to answer your question. But I think showing us your _run method might be helpful in helping solve this problem. I can give you a basic example of how one would do this with fork:

sub run {
    my ($self) = @_;
    my $PID = fork();
    # fork returns undef if it fails
    (defined $PID) || die "Could not fork successfully";
    # fork returns the Process ID of the new process it
    # has created to the parent process, and 0 to the 
    # child process, so if we have a "true" value in $PID
    # then we are in the parent
    if ($PID) {
         # so we let the parent store the PID
         # of the process which is "_run"-ning
         $self->{PID} = $PID
    }
    else {
          # otherwise we are in the child, so we
          # should call _run
          $self->_run();
          # we sure to call exit here so our child 
          # process cleans up nicely
          exit();
    }
}

# you can call stop from the parent
# process to kill the child, you can adapt
# this to send any number of signals to 
# the child depending upon your needs
sub stop {
    my ($self) = @_;
    kill "INT", $self->{PID};
}
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Here are a couple of links to relevant documentation:

• fork
• fork emulation info
• kill
• Signals