old:
do can throw or cause-error or return. return can be value, none, error, or unset
try converts error into return and thus can be either throw or return. return can be value, none, error, or unset
result won't set if throw
result can be return's value/error/none but unset causes error
attempt converts error into return and thus can be either throw or return. return can be value or none
so here's every possible flow:
test throws, try throws, result: unset, attempt throws, was-error: unset, everything dies from throw
   was-error: none? attempt [result: try [do "throw 5"]]
   throws => (unset? :was-error) and (unset? :result)
   limitation: it should instead handle this
test cause-error, try returns error, result: error, attempt returns error, was-error: false
   was-error: none? attempt [result: try [do "/"]]
   returns => (not was-error) and (error? result)
   bug: was-error should be true
test returns value/error, try returns value/error, result: value/error, attempt returns value/error, was-error: false
   was-error: none? attempt [result: try [do "5"]]
   returns => (not was-error) and (result == 5)
   correct
test returns unset, try returns unset, result: unset which cause-error, attempt returns none, was-error: true, everything dies when checking result
   was-error: none? attempt [result: try [do "unset 'a"]]
   returns => was-error and (unset? :result)
   bug: should handle this
test returns none, try returns none, result: none, attempt returns none, was-error: true
   was-error: none? attempt [result: try [do "none"]]
   returns => was-error and (none? :result)
   ~correct: was-error should be false. only currently "works" because of weird unless check

mine:
do can throw or cause-error or return. return can be value, none, error, or unset
do's return is ignored. if it returned then the block returns none
try/all converts throw and cause-error into return (as error)
result can only be none or error
was-error is true if do threw or cause-error. was-error is false if do returned at all
so here's every possible flow:
test throws, try converts to error, result: error, was-error: true
   was-error: error? result: try/all[do "throw 5" none]
   returns => was-error and (error? result)
   correct
test cause-error, try converts to error, result: error, was-error: true
   was-error: error? result: try/all[do "/" none]
   returns => was-error and (error? result)
   correct
test returns value/error, try returns none, result: none, was-error: false
   was-error: error? result: try/all[do "5" none]
   returns => (not was-error) and (none? result)
   correct
test returns unset, try returns none, result: none, was-error: false
   was-error: error? result: try/all[do "unset 'a" none]
   returns => (not was-error) and (none? result)
   correct
test returns none, try returns none, result: none, was-error: false
   was-error: error? result: try/all[do "none" none]
   returns => (not was-error) and (none? result)
   correct