You should learn and work toward mastery of at least three languages that are in high demand today, and keep an eye on emerging trends as you work toward graduation day -- not emerging hype, but real trends in the marketplace. Your livelihood will depend upon your adaptability to a dynamic environment. Keep your skills sharp, even those you aren't currently using. You never know when the floor is going to drop from beneath your feet and those skills might mean the difference between working as programmer and working as a busboy.

Here's the lowest-down: Your future employers are going to view you as a piece of thinking machinery whose purpose is to generate income for them. You are going to view your employers as big machines whose purpose is to generate income for you, so you have to have the right plugs and jacks to connect to that employer's cash flow. You have to be the right kind of machine, as does your employer. If your employer can find another machine that will generate more profit than you can, you will be replaced, just as you will replace your employer if another offers you more of whatever it is that you value most.

Directly addressing Perl: If it's Perl that inspires you, you'd be a fool not to pursue it. You'll learn more about programming if you work with a language that you truly enjoy than you ever will working with one that annoys you. If you have limited classroom time, devote that to whatever you believe is the most marketable language, and pick up Perl in your spare time after the homework is done and you're scoring As in the formal coursework. Then, after you're comfortable with and moderately proficient in Perl, add a third language that you believe is marketable and that you can enjoy working with. Why? Many jobs specify a given language as a requirement, with preference given to those applicants who can also work with other languages that are in use, usually in supporting roles.

UPDATE: If Perl is what you think will be the most marketable language, then go with it, and add those other two in your spare time. I don't mean to imply that Perl cannot be a good first choice.

FWIW, I'm self employed as a guy who tickles a keyboard all day discovering the magical keystroke sequences that will make money appear in my mailbox, and most of my time is spent writing in Perl. About a hundred families depend upon the work I do to keep them sheltered, fed, clothed, and well supplied with the conveniences and toys of modern life. It's certainly not a hobby for any of them, or for me and mine. I prefer Perl, but the job doesn't care about my personal preferences and if the need arises I will switch to C, C++, Java, or some other language that I'd have to learn or relearn to get the job done.

You've done one of the right things by seeking information about a chosen career from those who are actively working in the field. Teachers and guidance counselors are generally fine people whose opinions should be considered, but they're not actually working in the same world you're going to be launched into when they're done with you. Good job, thinking to come here!