Learn other computer languages in addition to Perl, and write a program that demonstrates your skill. I don't know nearly as much as you, but I could write a Perl program that does just about anything that any commercial software does. A few programs that demonstrate proficiency in Perl are enough to get an employer to take notice, but then there will be question like "Could I see your code?" and "Do you know (enter language here)?", which would be a problem. I've seen some of those adds too, and the skills those jobs require usually involve more than the ability to produce a certain program or fluency in Perl.