Let me get on my soapbox again 🙂
XlateInVals and XlateOutVals are lists and should be treated as such!!
With that said. Try this
# if phone number less than 10 characters, leave as is
set inph [lindex $xlateInVals 0] ;# Remove from list contex
if {[string length $inph] >= 10} {
regsub -all — {-} $inph {} inph
regsub — {(…)(…)} $inph {(1)2-} inph
set xlateOutVals