It's a wrapper around "lei q" which extracts Message-IDs
from URLs, "<$MSGID>", "id:$MSGID" and attempts to display the
local version of the message.
Its main purpose is to extract Message-IDs out of
commonly-understood URLs to save users bandwidth and time
by displaying the message locally. When reading from stdin,
it will discard things it doesn't understand, so you can just
pipe an entire "Link: $URL" line to it and it'll attempt to
pluck the Message-ID out of the URL.