At once and Handwriting-on-the-wall

At once adverb - Without delay or hesitation; with no time intervening.

Handwriting-on-the-wall and at once are semantically related. In some cases you can use "Handwriting-on-the-wall" instead an adjective phrase "At once".

At once and handwriting-on-the-wall are semantically related. Sometimes you can use "At once" instead an adjective phrase "Handwriting-on-the-wall".