Does the speaker really mean “alas!” or did they get “Wehe” as “woe” confused with the English expletive “Whoa!” Which would seem to fit the sentence better? Or is wehe doing double duty in German because it sounds like “whoa”?
“Wehe (dir)” is a threat, and it means “you better not” or the like.
I didn’t know “Woe!”, but my dictionary says it’s a possible translation. (and “wehe dir” would be “woe be to you”)
Small point regarding the English…Whoa, as far as I know is just an exclamation word to indicate surprise or hold on, similar to Damn or Jeez or one of those. Woe is a different word that could mean sorrow or things causing trouble or woes. “Woe be to you” seems like a funny archaic way of expressing “wehe dir” as in “woe be to you, for speaking to me again in that tone” as in, you are about to experience woe for that insolent tone of yours.
Woe and weh(e) are cognates. So in English it has become archaic while in German it has stayed normal in this fossilized form.
Wiktionary also gives “don’t you dare” as a translation.
It was just odd that “whoa” seemed to fit, as “Hold on! You can’t talk…” and I wondered if it was just one of those ‘adopted’ words, like 'sorry".
I thought the same thing about whoa, because coincidentally, it would fit the meaning. I did not know the meaning of wehe (thank you @pitti42) but then it was funny to see that it sort of means woe which can obviously be confused with whoa. Whoa nelly a lot of woe around! Just a suggestion, “woe be to you” has a slight Shakespearian or Biblical sound to it, “You better not be using that tone again!” would probably sound more contemporary.
At the risk of sounding foolish, it just struck me that wehe (dir) is probably related to weh, like “es tut mir weh”.