> my @uniq = keys %{ {%hash1, %hash2} };

From inside out:

- First the two hashes are flattened to lists, which are combined to a long list.

- Building a new (anonymous) hashref will eliminate duplicated entries from that hash ¹

- To be able to extract² the keys you still need to dereference this ano-hashref with %{..}.

step by step:

  DB<111> %hash1= (a=>1,b=>2)
 => ("a", 1, "b", 2)
 
  DB<112> %hash2= (a=>1,c=>3)
 => ("a", 1, "c", 3)
 
  DB<113> (%hash1, %hash2)
 => ("a", 1, "b", 2, "c", 3, "a", 1)
 
  DB<115> + {%hash1, %hash2}
 => { a => 1, b => 2, c => 3 }
 
  DB<117> %{ {%hash1, %hash2} }
 => ("c", 3, "a", 1, "b", 2)
 
  DB<118> keys %{ {%hash1, %hash2} }
 => ("c", "a", "b")

[download]

Cheers Rolf

UPDATES:

¹) because repeated keys will be overwritten.

²) at least with older perl-versions, see Athanasius' remark

In reply to Re: Syntax explanation required by LanX
in thread Syntax explanation required by ghosh123

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