Error# 6634 and 8284 and 7710

I will start with I am new to Fortran and to this forum so if there are any suggestions. Thanks in advance.  

My issue I that I keep coming across is error 6634 and 8284 when trying to use subroutines that operate on element operations.  I have created a simple routine to hopefully illustrate my problem as my code is too large to include. 

I have also included my workaround for Error 7710 related to passing a section of an array and wanted to know if there is a better workaround or best practice?

    program Test_Scale_Array

    implicit none

    ! Variables
    REAL(KIND=8), Dimension(:), Allocatable :: var3
    REAL(KIND=8), Dimension(1:10)           :: var2,exponent
    REAL(KIND=8)                            :: var4
    integer,      Dimension(5)              :: x
    integer                                 :: i

    ! Body of Test_Scale_Array
    var2     = 4.0D0
    var4     = 4.0D0
    exponent = 2.0D0
    !have routine that is meant mostly for this
    call simplesquare(var2,exponent)

    !Gives Error 8284 & 6634
    call simplesquare(var4)

    !Gives Error 6634
    call simplesquare(var2(2),exponent(2))


    !Selection and calculation on a portion of array
    x = (/(2*i,i=1,5)/)

    !Gives error #7710
    call simplesquare(var2(x))

    !Is there a faster/better way for the workaround?
    Allocate( var3(1:5) )
    var3 = var2(x)
    call simplesquare(var3)
    var2(x) = var3
    deallocate( var3 )

    contains

    subroutine simplesquare(x,y)
    ! Variables
    REAL(Kind=8), Dimension(:), INTENT(inout) :: x
    REAL(Kind=8), Dimension(:), OPTIONAL      :: y

    ! Body of simplesquare
    if (present(Y)) then
    x = x**y
    else
    x = x**2
    endif

    end subroutine simplesquare

    end program Test_Scale_Array
    

Thanks

Jim