>>Can't really use English to spell this out, because there are several ways to pronounce a single u (i.e. without pairings like ou, au, ue, ur) - there's the uh, as in umbrella, upsize, numb, then the yoo as in use, union, unicorn, and this u as u as in butcher, pudding, cushion (not everywhere!). I think there was a fourth way in some words, but can't remember it.
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>Loerkin' [lurking] ?

As I said already, with an ahr being the next letter, it's a whole new case, and no vowels keep their identity in that case, they all behave differently from other cases.

But my French-speaking daughter came to the rescue with an exmple: upanishad. That's where the u is pronounced as before the vowel shift, and it's the first character.