> P.S. This is also sure to upset the eval haters :)

Trouble is rather that you might end with a bug depending on input if you try increment a hashref.

I would prefer 


  DB<41> $ref= $tree

  DB<42> x @keys = split /@/,'a@b@c'
0  'a'
1  'b'
2  'c'
  DB<43> $ref = ($ref->{$_}//={})for @keys

  DB<44> x $tree
0  HASH(0xaa630cf0)
   'a' => HASH(0xaa6204a0)
      'b' => HASH(0xaa6719b0)
         'c' => HASH(0xaa75baa0)
              empty hash
  DB<45>

[download]

Update
And so on for each line 
DB<45> x @keys = split /@/,'a@b@d'
0  'a'
1  'b'
2  'd'
  DB<46> $ref= $tree

<= ($ref->{$_}//={})for @keys

  DB<48> x $tree
0  HASH(0xaa630cf0)
   'a' => HASH(0xaa6204a0)
      'b' => HASH(0xaa6719b0)
         'c' => HASH(0xaa75baa0)
              empty hash
         'd' => HASH(0xaa672e30)
              empty hash
  DB<49>

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re^2: creating the hierarchy pattern from the input file by LanX
in thread creating the hierarchy pattern from the input file by pruthvik

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