Only problem with that alias Solo you need to provide the file extension for $script([file]) to work. So a better way do it if you were going to do this is:

alias lowercase {
  if ($script($1)) {
    echo $color(info) -a *** Converting $1 now...
    %file.tmp = $+($gettok($1,1,46),-lc.,$gettok($1,2,46))
    if ($isfile(%file.tmp)) { write -c $v1 }
    filter -fk $1 convert
    unload -rs $1
    .remove $1
    filter -ff %file.tmp $1
    .remove %file.tmp
    load -rs $1
    echo $color(info) -a [End - Conversion]
    unset %file.*
  }
  else { beep 2 | echo $color(notify) -a *** Error - $1 was not valid }
}
alias -l convert { write %file.tmp $upper($1-) }