I set the tns_admin variable for the oracle7 user and got this

bash$ export TNS_ADMIN=/development/usr/local/oracle/product/7.3.4/network/admin/
bash$ echo $TNS_ADMIN
/development/usr/local/oracle/product/7.3.4/network/admin/
bash$ lsnrctl start

LSNRCTL for Solaris: Version 2.3.4.0.0 - Production on 31-AUG-01 14:04:21

Copyright (c) Oracle Corporation 1994. All rights reserved.

Starting /development/usr/local/oracle/product/7.3.4/bin/tnslsnr: please wait...

TNSLSNR for Solaris: Version 2.3.4.0.0 - Production
NL-00462: error loading parameter file /var/opt/oracle/listener.ora
NL-00427: bad list
NL-00427: bad list

If I do this for the ORACLE8 user I can start the listener.

Strange!