error module can be divided into error handling
functions and error evaluation functions.
All error handling functions concatenates the given arguments together with the : separator string between them.
juf_err_fat [ARGS...]
stderr and exits the current process.
juf_err_err [ARGS...]
stderr.
juf_err_warn [ARGS...]
stderr with the text "warning"
preprended.
Only one error evaluation function exists by now:
juf_err_tclmsg
and generates an
appropriate error message.
if {[catch "open [lindex $argv 0]" fileid] != 0} {
juf_err_fat [lindex $argv 0] [juf_err_tclmsg]
}