The my() declares the scope to the varaible and not the type. The type doesn't change.* In your example the variables will remain an array, a hash and a scalar no matter what you put into them.

Perhaps what you are really asking is whether there is any advantage of initialising variables like this. As far as I know there is no substantive difference between the two of these:

    my @array;
    my @array = ();
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However, you can gain some performance increase by pre-extending an array or a hash if you know what size it is likely to be:

    my @array;
    $#array = 99;
 
    my %hash;
    keys %hash = 100;
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--
John.

* Leaving arguments about bless() aside.