{ ==caller ==data
  "coroutine 1" dump data dump
  data caller 1 ! =caller =data
  "coroutine 2" dump data dump
  data caller 1 ! =caller =data
  "coroutine 3" dump data dump
  data caller 1 !
} !! ==cr

"data"
cr 1 ! --
"here 1" dump
cr 1 ! --
"here 2" dump
cr 1 ! --
"here 3" dump

0 sys .exit