I really want to be indispensible

I've been there - on both sides of the fence. It doesn't work. Noone is indispensible. The world doesn't end if you're hit by a bus - let alone if you leave. No matter what mess you create, someone will figure it out, or rewrite it. The only one knowing Perl at the company certainly doesn't make you indispensible. Someone else can always learn. Or hired. Or your work can be replaced by a Java program.