What are subroutines in Perl?

Perl is a flexible, object-oriented language that allows you to create and define your functionsuser-defined.

Subroutines are blocks of code that can be reused across programs. They are the same as functions or user-defined functions in Perl.

We can either define a subroutine in the same program or import it from another file using the use, do, or require statements.

Syntax

Generally, we can define a subroutine by following the syntax below:

# Function/Subroutine definition
sub subroutine_name {
  ...
  ...
  #statements the subroutine will execute
}

# Calling a subroutine
subroutine_func();

We have to write the sub keyword before defining the subroutine in the program.

Subroutines and arguments

We can pass several arguments to a subroutine, such as:

• Lists
• Hash
• Arrays
• Values
• Variables

Code

Passing variables, arrays, lists, and hashes as arguments

The following code snippet shows how to pass an array as an argument in a subroutine.

We use the symbol ($_) to pass single variable arguments in a subroutine, and we use the (@_) character to pass argumentssuch as arrays, hashes, and lists.

Explanation

The code snippet above displays how to pass and print different arguments from subroutines in Perl.

From line[1] to line[12], we can see that subroutine_variable actually swaps the values of $var and $var2.

The subroutine_array includes a printf statement with the symbol (@_) that accepts arguments as array indices in line[38].

subroutine_list accepts the same symbol (@_) as an array to pass arguments as parameters – it consists of a @list variable that includes two parameters: an array (@str1) and a scalar variable ($var).

subroutine_hash works when we pass a key along with a value as parameters into it. This subroutine includes a for each loop that iterates and prints the key-value pair in every statement.