DB<109> @arcb = ( 450, 625, 720, 645 );
 => (450, 625, 720, 645)
 
  DB<110> @arca = ( 625, 645 );
 => (625, 645)
 
  DB<111> @arcb{@arcb}=();
 => (undef, undef, undef, undef)
 
  DB<112> @arca{@arca}=();       # EDIT: ehm ... sorry useless line... 
 => (undef, undef)
 
  DB<113> delete @arcb{@arca}
 => (undef, undef)
 
  DB<114> @arcb=keys %arcb
 => (450, 720)