1 - it's trying to match the regular expression on the line starting $string =~ ... against the string found on the previous line.

2 - I'd start with #include <stdio.h> and #include <stdlib.h>. Maybe I'd also have #include <sys/types.h> and #include <regex.h>. I wouldn't start with #! /usr/local/bin/perl, and I definitely wouldn't start with #! /usr/local/bin/perl5.003 -w. I think the C preprocessor would take deep offense at either of those.

Finally, I'd get on to reading my course material. Most of my professors asked questions right out of the course material. When I finally figured that trick out, it was my last year, and my GPA shot way up.