in reply to Reverse regexp a regexp?

Higher Order Perl has the solution to (1) in Chapter 6.

6.5 Regex String Generation

Here’s a question that comes up fairly often on IRC and in Perl-related newsgroups: Given a regex, how can one generate a list of all the strings matched by the regex? The problem can be rather difficult to solve. But the solution with streams is straightforward and compact.

Update: added clarification

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

In Section Seekers of Perl Wisdom