An interesting sort problem

[jd1008]

The sort command does not provide for a way to say that the key is the 
last word in a line,
where the file contains lines of varying number of words,
and where words are groups of characters without spaces or tabs.

Thus

sort -k <what should this position be> <filename> ....

How can one tell sort to chose the last word in the line as the sort key?

The key is always the entirety of the last word.

Cheers,

JD