All these 14 Q's are from my last year exam paper i took from library and i am trying to solve them

Thank you for frankly explaining where these questions are coming from. Rather than explicitly answering them, I will give some quick pointers into the docs. Some of these questions are unclear to me; whether that is a problem with your transcription or the original, I cannot say.

1. Describe the main features of perl .What are its characteristics which makes it suitable for Bioinformatics

   perlintro, http://www.bioperl.org/wiki/HOWTO:Beginners

2. What is a file handle ? How they are similar to streams

   perlopentut

3. What are scalar variables ?Discuss various types of variables used in perl with examples.

   perldata

4. Describe named Unary and file operators with examples.

   perlop

5. Write a perl program that asks the user to enter a name and a number n and prints the nth letter in the name.

   Hint: substr

6. what are global and scoped declarations in perl ? Write perl script to explain the same .

   Declarations in perlsyn

7. How we do loop control with next last and redo ? Where we should use them and where not ?

   Loop Control in perlsyn, redo, last, next

8. What are regular expressions ? Explain in detail its most important elements ?

   perlre, perlretut

9. Write a perl program which takes file name as arguments and counts lines in file with (a) Letter X (b) String the

   Everything you need is in the above links

10. What are subroutines ? How it differs from a procedure ? Explain with example how parameters are passed in subroutines.

    perlsub

11. Write a perl program which reads a file into a hash array.

    Everything you need is in the above links

12. Write a perl script which compares and concatenates two strings.

    Everything you need is in the above links

13. What for formats are used in perl ? How we can access formatting internals ?

    I do not know what this means; do they mean perlguts or perhaps sprintf? Maybe IO Layers?

14. What are hashes ? Describe all functions relevant to hashes.

    perldata

If you are preparing for a test, where you found an old test in the library, your new test will likely not have the same questions on it; by gaining familiarity with the Perl documentation, you will prepare yourself for the next test, not the previous one.