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tcl function: editfile $script
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keyboard equivalent: none

The "EDIT" button on the "tcl:" entry line edits
the tcl script named in the entry to the left
using a basic editor (tries TextEdit, gedit,
nedit, xedit in that order).

To cause the editor to be vi inside a popped-up
gterm or xterm, set this environment variable:

  setenv CSURFEDITORVIGTERM
         *or*
  export CSURFEDITORVIGTERM=1
