procmail. query use of trailing :

[Ian Balchin <inksi@imaginet.co.za>]

Hi,

Why should i, or why should I not, use the trailing : in the first
line of a procmail recipe?

I know this is to do with a lockfile, but do not understand the whys
and wherefores of same.

:0:
* ^TOscuba
scubafile


:0
* ^From.*peter
* ^Subject:.*compilers
petcompil

both examples from man procmailex.  Even if the second example has
two conditions to be satisfied, why does it dispense with the
trailing : ?

Regards
Ian

-- 
Ian Balchin
http://www.imaginet.co.za/fables
This machine is running Debian GNU/Linux ... http://www.debian.org