Perl Interview Questions and Answers for 7 years experience

1. What are the differences between `my`, `local`, and `our` variables in Perl?

   • Answer: `my` creates lexically scoped variables, visible only within the block they are declared in. `local` creates dynamically scoped variables, temporarily overriding variables in the current scope. `our` declares package variables, accessible throughout the package.

2. Explain the concept of references in Perl. Give examples.

   • Answer: References are pointers to data structures. They allow you to create complex data structures and pass them efficiently. Examples include scalar references (`\$scalar`), array references (`\@array`), hash references (`\%hash`), and code references (`\&subroutine`). Example: `$ref = \@array;` creates a scalar reference `$ref` pointing to the array `@array`.

3. How do you handle errors and exceptions in Perl?

   • Answer: Perl uses the `eval` block to handle exceptions. `die` throws an exception, and `eval` catches it. You can also use `try`/`catch` blocks with modules like Try::Tiny.

4. Describe different ways to read a file in Perl.

   • Answer: You can read a file line by line using `while (<>) { ... }`, read the entire file into an array using `@lines = `, or read it chunk by chunk using `read` for better memory management with large files.

5. Explain the use of regular expressions in Perl. Provide an example.

   • Answer: Perl's regular expressions (regex) are powerful tools for pattern matching and text manipulation. The `m//` operator is used for matching, and substitutions are done with `s///`. Example: `if ($string =~ m/pattern/) { ... }` checks if `$string` matches `pattern`.

6. What are Perl modules and how do you use them?

   • Answer: Perl modules are reusable code libraries. They are used with the `use` or `require` statements. `use` imports functions and variables, while `require` just loads the module. Example: `use strict; use warnings; use DBI;`

7. How do you create and use custom Perl modules?

   • Answer: Create a file with a name matching the module name (e.g., MyModule.pm) containing the code. The module should have a package declaration (e.g., `package MyModule;`). Use `package` and `sub` to define functions. Export functions using `@EXPORT_OK`.

8. Explain the difference between `print` and `printf` in Perl.

   • Answer: `print` outputs data to the standard output, while `printf` allows formatted output similar to C's `printf`. It uses format specifiers to control the output's appearance.

9. How do you work with databases in Perl? Mention any modules you've used.

   • Answer: The DBI (Database Interface) module provides a standard way to interact with various databases. DBD::mysql, DBD::Pg, etc., are database-specific drivers used with DBI.

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

    • Answer: Perl supports OOP through packages, bless, and methods. Packages define classes, `bless` creates objects, and methods operate on objects.

11. Describe your experience with CGI programming in Perl.

    • Answer: [Detailed answer describing experience with CGI, including specific modules used, challenges faced, and solutions implemented.]

12. How do you handle command-line arguments in Perl?

    • Answer: [Detailed answer explaining the use of `@ARGV`, Getopt::Long or other argument parsing modules.]

13. What are some common Perl idioms and best practices?

    • Answer: [Detailed answer listing and explaining common idioms and best practices, such as using `strict` and `warnings`, proper variable scoping, effective use of references, etc.]

14. Explain how you would debug a complex Perl program.

    • Answer: [Detailed answer outlining debugging strategies, including the use of `print` statements, debuggers like `perldebug`, and logging.]

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