$ cat roundtrip.p6
compreg $P0, "Pugs"
$S0 = "say qq[There... and back again!]"
$P0 = compile $P0, $S0
$ ./pugs roundtrip.p6
There... and back again!
Once PGE has the ability to invoke callback code from the rules,
it can then call back to Pugs directly, and hence finishes the
basic circle needed for full bootstrapping.