use Perl

Subway "T" tokens in Boston cost $1.25. It's still cheaper for me to buy tokens as I go than to buy a commuter pass since I only take the train around 4-6 times a week. Lately I've developed a habit of leaving purchased tokens at home, so when I went to purchase tokens yesterday with a ten-dollar bill, I figured that I'd only need four, not eight.

Here's what happened:

1. I walked up to the booth next to the turnstiles and slipped my $10 bill under the glass. I said, "Four, please," with good articulation and volume to avoid confusion -- a touristy faux pas.
2. The following mix of currency and tokens was pushed back toward me:
   • 4 brass T tokens
   • 2 Sacagawea golden dollar coins
   • 1 Susan B. Anthony dollar coin
   • 1 $2-dollar bill
   • 1 $1-dollar bill

For those of you not in America, the only part of the above that people typically trade is the $1 bill -- at least, where I live. Golden dollars are unpopular. The $2 bill? Hell, there's even urban legend about the service industry thinking that they're fake.

Because I was busy talking to a friend on the ride to school, I didn't fully understand what had happened until I got there. The only logical explanation is that the T attendee recognized my inner nerdiness via scent. He must have decided to test my automata knowledge by presenting a denomination whose correctness can only be calculated in polynomial time.

I figure the extra dollar makes up the the tens of dollars the stupid token machines have eaten over the years, anyway.