But I was having problems and just tried returning the hash ref of each branch.

delete $node->{$doomed_key};
# recurse through remaining elements
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I just wanted to assign the hash structure of value into hashdata so I can use the %HashData normally in the main program.

That's fair enough: but you don't need to muck around with copies to achieve that. If in the caller code you have %Hash, and call your function with an argument \%Hash, any changes made indirectly to that data will show up in the caller. This is one of the main features of references.

Do you mean i should use shift?

It's a matter of style, so there will be differing opinions, but generally you can use my ($arg1, $arg2, ...) = @_ to get your parameters. (Sometimes shift is more appropriate, and sometimes even $_[0] etc. are the Right Thing -- but not typically.)

Ahhhh, I almost forgot about the @_ way ! I was making copies of the Hashes before for creating a function to replace key values within the hash dimensions.