Take a look at Perl regular expressions. There you'll find the information you need to get you started on regexps.

So, you have a regexp in that piece of code, and the and next; part is saying that, if the line that was read matches that condition, then you don't want to execute the rest of the code inside the while statement, you want to read a new line from input, meaning that the next code to be executed is while (<input>). That is to say, you go for another cycle of the while loop.