"Al pergum iter torum" isn't a thing; probably they meant "ad" and not "al," to start with.
"Ad" is "toward," while "pergum" is probably "pergam," which is also is "toward;" "iter" is a "journey," and "touruhm" is almost certainly a transliteration of "Torum," which is "a Bed..." but the connotation is for marriage/fucking, and not really for resting, per se.
So, while the author might want to say "may your next journey be restful"
... It's really almost saying "go get fucked." 😨
Which is almost a small bit humorous, except the context is so damn sad.