Array-only version of startsWith and skipOver

[Per Nordlöw]

On Friday, 25 October 2019 at 06:59:07 UTC, Per Nordlöw wrote:
> /** Array-overload for `skipOver` with no explicit predicate 
> predicate. */
> bool skipOver(T)(scope ref const(T)[] haystack,
>                  scope const(T)[] needle)

Found it.

The parameter `haystack` must be qualified with inout instead of 
const because it's `ref`.

bool skipOver(T)(scope ref inout(T)[] haystack,
                  scope const(T)[] needle)
{
     if (startsWith(haystack, needle))
     {
         haystack = haystack[needle.length .. $];
         return true;
     }
     return false;
}

Why?