wrong password accepted

Hi,

this is a strange situation I just discovered on a postgresql
7.2.1-2woody2 (Debian as you can see...). I use pg_hba to specify
password ahtentications for clients. HEre's the line:
host         all         127.0.0.1    255.255.255.0       password  pass-file

I just discovered that when I use the correct password to whach I append
text, it is accepted (though this is not correct...)
For example, if my password is postgres, the following will also be
accepted: postgresql, postgresblabla, postgres2 ...... but it will
reject postgrex eg.

I couldn't reproduce it with postgres 7.3 (self compiled, the problem
above happens with the standard Debian package), but 7.3 doesn't seem to
use a file to store the password (didn't have time to look a lot at 7.3 :(.

Is this a known problem? Did I miss the answer when I browsed the web
and mail archives?

Thanks for your help.

Raph