The first step is to review your course material. It is quite unlikely that your teacher gives you homework that cannot be answered by the course material you have worked on so far.

Is PM a good place to get answers for homework?, How do I post a question effectively?, PerlMonks FAQ

Whether this is homework, real work, or personal learning, you will probably get better responses if you show some effort. This is not a code writing service.

If you would instead prefer to have someone else's answer, try the google monster. You will, however, have forfeited much of the learning opportunity attempting to solve this yourself would provide.

sorry guys .. I am trying to learn based on examples , instead of reading books .

sorry guys .. I am trying to learn based on examples , instead of reading books .

Books contain examples, and explanations of examples :)

perlintro, perlretut, perlrequick are all about examples

bharatbsharma:

You can read the documentation for perl's regular expressions by typing perldoc perlre at the command line. You'll probably also want to read perlretut and perlrequick.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

A2: How are the clauses to be taken? Disjunctions? Conjunctions? Juxtapositions? The latter seems the most logical, but then, why not just use "followed by", which is used on clauses a) and b)? And since clause b) matches any string, disjunctions seems unlikely. Leaves us conjunctions. But then the answer ought to be: it's better done with three regular expressions.

A2: How are the clauses to be taken?

I think it are three separate questions a), b) and c).

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

I think it are three separate questions a), b) and c)

That's what I initially thought as well. But the question states a regular expression, not regular expressions. It also means the teacher likes trick questions, as the answer to b) is any pattern that matches the empty string. It doesn't mean you're wrong - I just didn't find it likely.