Function Intersperse

Part of:

package weblocks
( intersperse < list > < delimeter > &key (last delimeter) )
Intersperses a list with a delimeter.

If 'last' is specified, it will be used for the last delimeter,
instead of 'delimeter'.

(intersperse '(1 2 3 4 5) 0)
=> (1 0 2 0 3 0 4 0 5)