document: chunk(s?) /\z/
chunk: open chunk close | word(s)
open: "<open>"
close: "<close>"
word: /\w+/

##</code><code>##

document: stuff /\z/ { return $item{stuff} }
stuff: chunk(s?) { return [map {@$_} @{$item[1]} ] } # flatten adjacent arrayrefs
chunk: open stuff close { return $item{stuff} } | word(s?) # returns arrayref
open: "<open>"
close: "<close>"
word: /\w+/