[f|~/code/perl/homework]% perl physics.pl 
---Welcome to the Physics Master Key.

> a = 12
> print vars
a is 12
> F1 = 12
> F2 = 53
> m1 = 3
> m2 = 6
> print vars
F1 = 12
F2 = 53
a is 12
m1 = 3
m2 = 6
>