According to the lib documentation, the list of directories passed to lib are added to the start of the list - That is saying:

use lib LIST;
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is equivalent to

BEGIN { unshift(@INC, LIST) }
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And as such the directory specified will be searched first, rather than last as you suggest.

I suggest you look at the list which you are passing to lib and also look at what values are contained in @INC immediately prior to your use CGI statement.

 

Update

Another interesting module which you may want to look at FindBin whose documentation you can find here which allows library directories to be based upon the script location.

 

perl -e 's&&rob@cowsnet.com.au&&&split/[@.]/&&s&.com.&_&&&print'