reusing choroba's rindex idea, here a debugger demo using substr instead of a complicated regex (the p are just for printing the preliminary results)

  DB<34> $string = "hello my * name is Rob * and * I am a very nice pe
+rson * at least * I think * so"

  DB<35> p $pos = rindex $string, ' * ', 30
28
  DB<36> p $left = substr $string, 0, $pos+3, ""
hello my * name is Rob * and *
  DB<37> p $string
I am a very nice person * at least * I think * so
  DB<38> p "<$left>"
<hello my * name is Rob * and * >
  DB<39>
[download]

please note the trailing whitespace in $left