Jump to a local label within an SFK script by sfk goto.

sfk goto label

jump to a local label within the command chain.

A local label means:
- no +end is allowed between goto and the label.
  use +stop instead to interrupt execution.
- the label must start like +label name,
  but not like "sfk label name".

The very last command of the overall command chain
must be followed by +end.

Note: chain data flow may get broken!
in a command chain like
   echo ... +goto ... +echo ... +xed
SFK cannot decide if the first echo should
send data to xed, so normally chain data
transfer is broken by goto, and needs to be
worked around by +storetext and +gettext like:
   echo ... +storetext +goto ... +gettext +xed

see also
   sfk call        call a global label
   sfk storetext   store whole chain data
   sfk gettext     recall stored chain data

   --- file dofilter.bat: ---
   sfk script %0 -from begin %1
   GOTO xend
   sfk label begin
      +if "%1 = " goto help
      +echo "got filename: %1"
      +then filter %1 -+foo
      +stop 0
      +label help
         +echo "usage: dofilter.bat filename"