Yes, he clearly should have taken into account any possible subunit denomination, including exotic native tribe money units like sea shells, because international programmers reading HN are not expected to think of that of their own.
Such vitriol! Can your currency code handle sea shells? It should! :)
I only mention it because the yen thing surprised me once as a newbie programmer. (A tip: "%0.2f" is no substitute for actual i18n.) It never hurts to be aware of the edge cases.
The yen has no fractional units (anymore), so when I added support for that currency but continued to use the same format string as all the others, prices like ¥1000.00 looked unnatural.
The historical subunit of the yen is the "sen" (銭), which you often seen mentioned in prewar books. Postwar inflation made sen-denominated currency obsolete, but...
[A bit of googling also turns up the "rin" (厘), which is a thousandth of a yen...]
