Each array element should be a key except for the first

Maybe I had misread this line when I wrote my previous answer. Possibly you really want something like this: 

$hash1{$_}++ for @elements;

[download]
Example under the debugger: 
  DB<1>  @elements = qw/ 1 3 5 4 6/;

  DB<2> $hash1{$_}++ for @elements;

  DB<3> x \%hash1
0  HASH(0x600509af0)
   1 => 1
   3 => 1
   4 => 1
   5 => 1
   6 => 1

[download]

In reply to Re^3: Hashes, keys and multiple histogram by Laurent_R
in thread Hashes, keys and multiple histogram by f77coder

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