Please ignore spectre9's post completely.
No conversion/casting is done when assigning a scalar to a scalar (such as an array element).
No conversion/casting is done when assigning a list to an array.
There's no requirements for all elements of an array to be of the same type.
Existing elements have no effect on elements added to an array.
You could have spent five seconds checking to find out that the + is acceptable instead of spending the time saying it might not be.
>perl -wle "print 1E+04"
10000
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