" :force <expr> print <expr>, forcing unevaluated parts\n" ++
" :forward go forward in the history (after :back)\n" ++
" :history [<n>] after :trace, show the execution history\n" ++
+ " :list show the source code around current breakpoint\n" ++
+ " :list identifier show the source code for <identifier>\n" ++
+ " :list [<module>] <line> show the source code around line number <line>\n" ++
" :print [<name> ...] prints a value without forcing its computation\n" ++
" :sprint [<name> ...] simplifed version of :print\n" ++
" :step single-step after stopping at a breakpoint\n"++