S. R. Faruqi:

The jugular vein is a thick vein; but since life is known to depend on it, it is also considered to be delicate. The beloved's curl is more delicate, and also has radiance. The word tāb has two meanings, 'radiance' and 'tangled up together'. Both meanings are suitable here. There's also a Persian idiom tāb dādan , which means 'to cause to flare up', 'to cause to shine', 'to make sharp', 'to tangle a rope or thread'.

Another point is that the jugular vein is the sustainer of life, so it's also precious to everyone. Here a single strand of the beloved's curls is equal to a hundred jugular veins; that is, it's as life-giving and precious as a hundred jugular veins. There's also an affinity of tāb meaning 'shine' and tār meaning 'darkness', as if the blackness of one strand of the curls is equal to the shine of a hundred jugular veins.

FWP:

SETS == GROTESQUERIE; MULTIVALENT WORDS ( tāb )
MOTIFS == [BELOVED IS NOT GOD]; CURLS
NAMES
TERMS == AFFINITY

It's also enjoyable that the unspecified subject, presumably God, didn't just combine a hundred jugular veins with their pre-existing, surely substantial amounts of tāb . On the contrary, in fact: he took them up and 'gave' them some kind or degree of 'mutual' tāb that they hadn't had before. Perhaps this means he twisted them together, like a rope, for strength. Or perhaps it means that he made them more dazzling (for the fine wordplay with tār ), or more twisting, or more powerful, or more deadly. (Or perhaps, of course both.) Only then were they worthy to become a single strand of the beloved's tangled, all-ensnaring curls. The remarkable multivalence of tāb (see the definition above) is deployed to full advantage here. For another such masterful use of tāb , see {1237,5}.

The 'hundred jugular veins' image, in its novelty and ingenuity, is what really makes the verse. It also, of course makes the verse grotesque, if we take the image too literally. It makes the beloved sound like Medusa, with her thick writhing snakey curls.