Perl and SQL are languages created to do totally separate things, so converting SQL to PERL really wouldn't be all that useful.

However using PERL and SQL together can make your jobs a lot easier and can also lighten the load on your SQL server. Compiling large amounts of data and having SQL do processing on all of the records, which on heavily used database servers, can slow the server a lot, which can be a problem especially with CGIs which will timeout. Instead you can do the data processing in PERL, which will free up some processing time on the database server. Not to mention huge SQL queries are just a pain to begin with.

This is just from personal experience, where we had many database servers brought to their knees by programmers who didn't take advantage of perl's data processing power.