If you don't know the size, you can determine at run time by looking. You can always determine the size of an array. If all the referencing is not clear, dereference in multiple steps. Maybe read perldsc, try something new, and/or ask different questions.

# Get the size of data1
my $sizeOfData1 = scalar @{$data1};
print $sizeOfData1;

# Enumerate over each element, a hash reference, of data1
for my $hashref (@{$data1}) {   # Dereference the array
    my %realHash = %{$hashref}; # Dereference the hash
}
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