???

[GasQueen]

Could someone explain this to me please?

function Init takes nothing returns nothing
    set x[0] = 50
    set x[50] = 25
    set x[25] = 75
    set x[75] = 100
    set x[x[x[x[x[0]]]]] = 95
    call PrintInt(x[100])
endfunction

What's the meaning of arrays variables having indexes as arrays variables?

 

[Dr Super Good]

The index of an array is an integer. It can be any statement that returns an integer.

In this case, as the array is an integer array, its own elements can be used as an index to an element.

In this example, when the game runs it it will evaluate like this....
set x[x[x[x[x[0]]]]] = 95
get value at x[0]
set x[x[x[x[50]]]] = 95
get value at x[50]
set x[x[x[25]]] = 95
get value at x[25]
set x[x[75]] = 95
get value at x[75]
set x[100] = 95
Make value at x[100] become 95

Other valid indecies are '0000' formated integers and function calls.