Try to use select with a small timeout value.
Maybe you can use also the perl implementation of ioctl that allow you to do non-blocking i/o ( among many other things )

Update :

It's also possible to handle the "IO" signal by linking some function to $SIG{IO} sighandler, and play with the filehandle's flags with fcntl

No more details : searching is the way of understanding...

Hope this help :)