This should allow you to try out a perl regular expression. You could write a simple perl program to do exactly the same thing, but this allows you to change things slightly to see how the results are affected. Give it a try!
After a (hopefully short) time, you should see the results of the match.
Just in case you don't know, here is a table describing what the different variables mean:
| $& | The text that that matched. |
|---|---|
| $` | The text that occurred before the text that matched. |
| $' | The text that occurred after the text that matched. |
| $n | The text that matched within the nth set of parens. (Count the open parens from left to right to figure out which is the nth set.) |