The phrase \$somevar escapes the dollar sign, avoiding interpretation of the variable in the command where the prompt is set. Instead, the interpretation occurs whenever the prompt is drawn.
For the first step, you should learn your shell's peculiarities, the way that Unix passes command-line arguments to Perl and Perl's interpretation of those arguments.
No doubt under a higher command, but its orders, which are more general, require interpretation by him and upon that interpretation depends the life of ten, fourteen or twenty men.