~<Esperanto>

$C = [pbtdkgmnfvszŝĵcĉĝĥhwjlr]
$V = [iueoa]
$_ = [⟨C⟩⟨V⟩]

* Invalid letters
  + ^ ⟨_⟩+ $
    ?+ scii
    ?! axa

* More than 5 consonants sequentially
  ! ⟨C⟩{6}
    ?+ ekssklavo
    ?! eksskrla