Sometimes having these set I still have a problem. What I have to do is run:

export LD_LIBRARY_PATH=$ORACLE_HOME/lib
export ORACLE_USER=username/password@SID
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right before you install the DBD for Oracle. Once you get it installed then you are going to want to add a line in your /etc/ld.so.conf file
This line will be:

/full/oracle/home/here/lib
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then save that file and run ldconfig. It will save you tons of headaches in the future.

--BigJoe

Learn patience, you must.
Young PerlMonk, craves Not these things.
Use the source Luke.