Perl Interview Questions and Answers for 5 years experience

1. What is Perl?

   • Answer: Perl is a high-level, general-purpose, interpreted, dynamic programming language. It's known for its powerful text processing capabilities, regular expressions, and its ability to glue different systems together.

2. Explain the difference between `my`, `local`, and `our` variables.

   • Answer: `my` creates lexically scoped variables, visible only within the current block. `local` creates dynamically scoped variables, affecting only the current subroutine and its callees. `our` declares package variables, accessible throughout the package.

3. What are references in Perl?

   • Answer: References are pointers to data structures. They allow you to create complex data structures like linked lists, trees, and hash of hashes. They are created using a backslash before a variable.

4. How do you handle errors in Perl?

   • Answer: Perl uses the `eval` block to handle exceptions. You can also check the value of `$?` after system calls to check for errors, and use `die` to terminate execution with an error message. Modules like Try::Tiny provide more structured exception handling.

5. Explain the use of regular expressions in Perl.

   • Answer: Perl's regular expression engine is very powerful. It's used for pattern matching and text manipulation. The `m//` operator performs pattern matching, and various modifiers control the matching behavior (e.g., `i` for case-insensitive matching, `g` for global matching).

6. What is the difference between `grep` and `map`?

   • Answer: `grep` filters a list, returning only elements that match a given condition. `map` applies a function to each element of a list and returns a new list with the transformed elements.

7. Explain the concept of modules in Perl.

   • Answer: Modules are reusable code units organized into separate files. They are used with the `use` statement and provide a way to organize and share code. They enhance code reusability and maintainability.

8. How do you create and use a custom module in Perl?

   • Answer: A custom module is created by placing Perl code in a file named `ModuleName.pm`. The module's functions are typically placed within a package declaration (`package ModuleName;`). It's then used in other scripts with `use ModuleName;`.

9. What is the purpose of the `use strict` pragma?

   • Answer: `use strict` enforces stricter coding practices. It requires explicit variable declarations (using `my`), prevents the use of barewords as identifiers, and helps to catch common errors early.

10. What are file handles in Perl?

    • Answer: File handles are symbolic names that refer to open files. They are used to read from or write to files. They are typically opened using the `open` function and closed using the `close` function.

11. Explain different ways to read a file in Perl.

    • Answer: Files can be read line by line using a `while` loop and the `<>` operator, or using `readline`. The entire file can be read into an array using `@lines = ;` or slurped into a single scalar using `$content = do { local $/; };`.

12. How do you write to a file in Perl?

    • Answer: Data is written to a file using the `print` function with a filehandle. For example: `print FILEHANDLE "My data\n";`.

13. What are hashes in Perl?

    • Answer: Hashes are associative arrays, where data is accessed using keys instead of numerical indices. They are declared using curly braces `%hash = ('key1' => 'value1', 'key2' => 'value2');`.

14. How do you iterate through a hash in Perl?

    • Answer: You can iterate using `foreach` with keys: `foreach my $key (keys %hash) { print "$key => $hash{$key}\n"; }` or using `each` for key-value pairs.

15. Explain the concept of object-oriented programming (OOP) in Perl.

    • Answer: Perl supports OOP through packages and blessings. A class is essentially a package, and objects are created by blessing a reference into a package.

16. How do you create a class and objects in Perl?

    • Answer: A class is defined by creating a package. Objects are created by blessing a reference to a hash or an array into the package using `bless`.

17. Explain inheritance in Perl.

    • Answer: Inheritance is achieved by having one class inherit methods and attributes from another using the `@ISA` array.

18. What are autoloading and method overloading?

    • Answer: Autoloading allows methods to be loaded only when they are called. Method overloading allows different methods to be called based on the number or type of arguments.

19. What are some common Perl modules you've used?

    • Answer: (This will vary depending on experience, but examples include: `DBI`, `DBD::Pg`, `LWP::UserAgent`, `CGI`, `Moose`, `Test::More`, etc.)

Thank you for reading our blog post on 'Perl Interview Questions and Answers for 5 years experience'.We hope you found it informative and useful.Stay tuned for more insightful content!