An array cannot be the key of a hash. Perl stringifies hash keys, so that hash keys are always strings. Even if you tried something like this: 
$hash1{\@elements}++;

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or 
$hash1{[@elements]++;

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it would not work, because your key would end up being a stringified array ref (and the array content would be lost).

So either you want to use the string that you've read to be the hash key 

$hash1{$line}++;

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but that does not seem to be very useful in this context, or you want to store an array reference into the value of the hash 
$hash1{"some key"} = \@elements;

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but then I am not sure what you would want your key to be.

I think you need to have (and provide us) a clearer idea of the data structure that you want to have at the end of your process.

Quite possibly you really need an array of arrays, rather than a hash of arrays. Quick demonstration under the Perl debugger: 

  DB<1>  @elements = qw/ 1 3 5 4 6/;

  DB<2> push @array, \@elements;

  DB<3>  @elements2 = qw/ 12 13 14 15/;

  DB<4> push @array, \@elements2;

  DB<5> x \@array
0  ARRAY(0x600509af0)
   0  ARRAY(0x600500b38)
      0  1
      1  3
      2  5
      3  4
      4  6
   1  ARRAY(0x600500928)
      0  12
      1  13
      2  14
      3  15

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Update: Perhaps I misunderstood your requirement. Please read my next answer on Aug 17, 2014 at 08:50 UTC (immediately below)

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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