Client installation: for anything that needs to talk to the Oracle server (in your case, the webserver).

• Install the Oracle *CLIENT* libraries and software on the client system. Pro*C and Pro*C++ should be what you need for DBD::Oracle. sqlplus isn't necessary, but it's nice to have for tracking connectivity problems down.
• make sure ORACLE_HOME and ORACLE_SID are set.
• install DBD::Oracle
• enjoy

As far as backing out failed installs: simply removing the .pm files from the perl module directory tree should work, but if you're using CPAN you can always use the "force" option to install over a broken installation.

perl -e 'print "How sweet does a rose smell? "; chomp ($n = <STDIN>); 
+$rose = "smells sweet to degree $n"; *other_name = *rose; print "$oth
+er_name\n"'
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