- [P] [B] while
- [P] [B] swap [nullary] cons dup dipd concat loop
- [B] [P] [nullary] cons dup dipd concat loop
- [B] [[P] nullary] dup dipd concat loop
- [B] [[P] nullary] [[P] nullary] dipd concat loop
- [P] nullary [B] [[P] nullary] concat loop
- [P] nullary [B [P] nullary] loop
+ [P] [B] while
+ [P] [B] swap [nullary] cons dup dipd concat loop
+ [B] [P] [nullary] cons dup dipd concat loop
+ [B] [[P] nullary] dup dipd concat loop
+ [B] [[P] nullary] [[P] nullary] dipd concat loop
+ [P] nullary [B] [[P] nullary] concat loop
+ [P] nullary [B [P] nullary] loop