Good point; bad oversight on my part. Below, I take extra effort to count only leading spaces...

use strict; use warnings;
AUTOLOAD{$.=0;$_=@_[$??$;:$.];@_=reverse
         split//;++$.while+pop=~m,\s,;y,
                ,     ,s,warn$.,$_,$/}&*
         ($_)for(<DATA>)
__DATA__
 Initiate
  Novice
   Acolyte
    Sexton
     Beadle
      Scribe
       Monk
        Pilgrim
         Friar
          Hermit
           Chaplain
            Deacon
             Curate
              Priest
               Vicar
                Parson
                 Prior
                  Monsignor
                   Abbot
                    Canon
                     Chancellor
                      Bishop
                       Archbishop
                        Cardinal
                         Sage
                          Saint
                           Apostle
                            Pope
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See also JAPH at the firing range