General answer : References quick reference.

More specific answer: $data{$formname} is an entry in a hash. The wrapping of the @{ ... } around it indicates that this hash entry is a reference to an array. What's being pushed onto the array is an anonymous hash (reference to a hash with no name).

Putting that together listily:

• $data{$formname} => reference to an array
  • dereference with @{ REFERENCE }
• $data{$formname}->[0] => the first element of that array. Perl lets you tighten that up to $data{$formname}[0]. The element of that array is a reference to a hash, so
  • dereference with %{ REFERENCE }
• $data{$formname}->[0]->{type} (also $data{$formname}[0]{type} ) => The value of the 'type' field in the anonymous hash. This is a normal scalar, and so needs no dereferencing.

So, to iterate over the keys of that (anonymous) hash, you might do

foreach my $key ( keys %{ $data{$formname}[0] } ) {
    print $key, " ", $data{$formname}[0]{$key}, "\n";
}
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HTH

If not P, what? Q maybe?
"Sidney Morgenbesser"