1. What is Perl?
Perl is a high-level, interpreted programming language that was designed for text-processing. It has powerful features like regular expressions and string handling.

2. What are the different data types supported by Perl?
Perl supports three main data types: scalars, arrays, and hashes. Scalars are single values like numbers or strings, arrays are ordered lists of scalars, and hashes are unordered collections of key-value pairs.

3. How do you define a variable in Perl?
In Perl, variables are defined by using the dollar sign ($) prefix. For example, to define a scalar variable called $name, you would write: $name = “John”;

4. What are regular expressions in Perl?
Regular expressions are powerful tools used for pattern matching in Perl. They allow you to search, replace, and manipulate strings based on specific patterns.

5. How do you open and read a file in Perl?
To open a file in Perl, you can use the open() function. Once the file is opened, you can read its contents using the readline() or syntax.

6. How do you print output in Perl?
You can use the print() function to display output in Perl. For example, print “Hello, World!”;

7. How do you pass command-line arguments to a Perl script?
Command-line arguments can be accessed in Perl using the special array @ARGV. The first argument is stored in $ARGV[0], the second in $ARGV[1], and so on.

8. What is the purpose of chomp() function in Perl?
The chomp() function in Perl is used to remove the newline character at the end of a string. It is commonly used when reading input from a file or the user.

9. How do you concatenate strings in Perl?
Strings can be concatenated in Perl using the dot (.) operator. For example, $name = “John” . “Doe”; will assign the value “JohnDoe” to the variable $name.

10. What is the difference between my and local variables in Perl?
The my keyword declares a variable with limited scope, while the local keyword makes a variable visible to other functions called within the same scope.

11. How do you check if a file exists in Perl?
You can check if a file exists in Perl using the -e file test operator. For example, if (-e “file.txt”) { … } will execute the code block if the file.txt exists.

12. What is the difference between print and say in Perl?
The print function in Perl prints output without adding a newline character, while the say function automatically appends a newline character at the end.

13. How do you sort an array in Perl?
In Perl, you can use the sort() function to sort an array. By default, it sorts strings alphabetically. To sort numerically, you can use the <=> operator.

14. How do you find the length of a string in Perl?
The length() function in Perl returns the length of a string. For example, length(“Hello”) will return 5.

15. What are filehandles in Perl?
In Perl, filehandles are used to associate a file or stream with a variable. They enable reading from or writing to a file, similar to file pointers in other languages.

16. How do you find the current date and time in Perl?
The localtime() function in Perl returns the current date and time as an array. You can access different elements like day, month, year, hour, minute, and second.

17. How do you make a substring in Perl?
The substr() function in Perl is used to extract a substring from a larger string. It takes the string, start position, and length as arguments.

18. How do you convert a string to uppercase in Perl?
The uc() function in Perl converts a string to uppercase. For example, uc(“hello”) will return “HELLO”.

19. What is the purpose of the -w flag in Perl?
The -w flag enables warnings in Perl, which helps in identifying potential errors or issues in the code during the compilation process.

20. How do you comment in Perl?
In Perl, a single-line comment starts with a hash (#) symbol. For multi-line comments, you can use the POD (Plain Old Documentation) syntax.

1. What are the differences between scalar variables, arrays, and hashes?
– Scalar variables hold a single value.
– Arrays store ordered lists of scalar values.
– Hashes store unordered lists of key-value pairs.

2. How do you define a subroutine in Perl?
In Perl, a subroutine is defined using the `sub` keyword followed by the subroutine name and the block of code.

3. What is the purpose of the `use strict;` and `use warnings;` pragmas in Perl?
The `use strict;` pragma enforces the use of variable declarations and scoping rules, making code more reliable. The `use warnings;` pragma enables additional warnings about potential issues in Perl code.

4. How can you execute an external command from within a Perl script?
By using the `system` function or by enclosing the command in backticks (`) or the `qx` operator.

5. Explain the concept of file handling in Perl.
File handling in Perl involves opening, reading, writing, and closing files. Perl provides various built-in functions and operators for file handling, such as `open()`, `close()`, `read()`, `write()`, etc.

6. What is the difference between `eq` and `==` when comparing two strings in Perl?
The `eq` operator is used for string comparison, checking if two strings are equal. The `==` operator is used for numeric comparison, checking if two numbers are equal.

7. What are Perl modules?
Perl modules are reusable packages of code that group related functions, methods, and variables together. They allow for code modularity and reusability.

8. What is a regular expression in Perl?
A regular expression, or regex, is a powerful tool in Perl for pattern matching and manipulation of strings. It allows for searching, replacing, and extracting specific patterns from strings.

9. How do you handle error conditions in Perl?
Error handling in Perl can be done using the `eval` function to catch exceptions, the `die` function to print error messages and terminate the program, or by using `try` and `catch` blocks using the `Try::Tiny` module.

10. How can you control the execution flow in Perl?
Perl provides various control structures like `if/else`, `for`, `foreach`, `while`, `until`, etc., to control the flow of execution based on conditions or loops.

11. What are autovivification and autoboxing in Perl?
Autovivification is a feature in Perl that automatically creates complex data structures when they are accessed. Autoboxing refers to the automatic wrapping of simple values into objects or complex data structures.

12. How can you handle command-line arguments in Perl?
The `@ARGV` array in Perl stores command-line arguments. You can access and process these arguments using this array.

13. Explain the Perl DBI module and its usage.
The Perl DBI (DataBase Interface) module is used to communicate with databases in Perl. It provides a common interface to access various database systems such as MySQL, PostgreSQL, Oracle, etc., and perform operations like connecting to databases, executing SQL queries, fetching results, etc.

14. What is object-oriented programming (OOP) in Perl?
Object-oriented programming is a programming paradigm that allows creating objects that encapsulate data and behavior. Perl supports OOP through modules like `Moose` and `Moo`.

15. How can you handle exceptions in Perl?
Perl provides exception handling using the `eval` function and the `die` function. You can catch exceptions using `eval` and handle them using a `catch` block.

16. What are closures in Perl?
A closure is a subroutine that has access to variables outside its immediate scope. It “closes over” those variables and retains their values.

17. What is the purpose of the `use` statement in Perl?
The `use` statement in Perl is used to load modules or pragmas into the current script, enabling the use of additional functionality or strict/warning features.

18. How can you handle multi-threading in Perl?
Perl provides various modules like `threads`, `threads::shared`, and `Thread::Queue` to handle multi-threading. You can create and manage threads using these modules.

19. Explain the difference between `my` and `local` variable declarations in Perl.
The `my` keyword is used to declare lexically scoped variables that are private to the current block or subroutine. The `local` keyword is used to temporarily override global variables, making them local to the current scope.

20. Can you use Perl for web development?
Yes, Perl can be used for web development. There are various Perl frameworks like Catalyst, Dancer, Mojo, etc., that facilitate web development in Perl. Perl also provides modules like CGI and PSGI for handling web requests and generating dynamic content.