The + is just to point the perl parser into the right direction see map. 
  %hash = map {  "\L$_", 1  } @array  # perl guesses EXPR.  wrong
  %hash = map { +"\L$_", 1  } @array  # perl guesses BLOCK. right
  %hash = map { ("\L$_", 1) } @array  # this also works
  %hash = map {  lc($_), 1  } @array  # as does this.
  %hash = map +( lc($_), 1 ), @array  # this is EXPR and works!

  %hash = map  ( lc($_), 1 ), @array  # evaluates to (1, @array)

               or to force an anon hash constructor use "+{"

   @hashes = map +{ lc($_), 1 }, @array # EXPR, so needs , at end

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Boris

In reply to Re: map + by borisz
in thread map + by palette

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