Re^4: How to build a hash?

[Ben Win Lue]

Sorry, maybe my use english is a bit confusing... 8-)
My problem was, I stored a reference to a hash (%hash_a) in a hash (%hash_b). Worked perfectly for one record.
Now, when i overwrote the contents of %hash_a, the contents in %hash_b where overwritten, too.
The whole stuff worked for more than one record only after I introduced the curly braces.

[davorg]

There are two ways to take a reference to a hash.

If you use the \%hash syntax then you are taking a reference to the _original_ hash. Any updates that you make through that reference will obviously update the original hash (as, actually, there is only ever one hash).

If you use the { %hash } syntax then you are creating a new anonymous hash which is a _copy_ of your original hash and getting a reference to this new hash. Any updates you make through this reference will update the copy of the hash and not the original hash.

I recommend reading "perldoc perlreftut" and "perldoc perlref" to clarify these concepts.