The original pagelisttrails cookbook entry appears to have not been updated
since November 2004, and is documented as broken since April 2005.
I've propagated the changes in PmWiki between then and now (Nov 2005), which
seems to have made it work again.
The original blockedit cookbook recipe only works for pmwiki version 1, and pmwiki2 has other facilities. However, I quite liked the old recipe, and it was quite easy to port over, so here it is.