Use of Perl Data::Dumper

The Dumper is a function of the Perl data module that is used to convert any type of the Perl data variable and print the content in the Perl format. Any Perl scalar variable or array variable or hash variable can be passed as the argument of the Dumper function and stores the output in the $VARn variable where the value of the “n” depends on the number of reference variables. The output of the Dumper function can be used as the argument of the eval() function. The Data:Dumper module is required to be included in the script to use the Dumper function.

Different Uses of the Perl Data::Dumper

The uses of the Dumper function to print the scalar variables, array variables, hash variables, and file content are shown in this part of the tutorial.

Example 1: Using the Data::Dumper for Scalar Variables

Create a Perl file with the following script that prints the values of the “string” variable and the “number” variable using the Dumper function:

Output:

The following output appears after executing the script. The string value of “Md. Ali” and the number of “35” are printed by the $VAR1 variable of the Dumper function. The number value is printed as a string value in the output:

Example 2: Using the Data::Dumper for the Array Variable

Create a Perl file with the following script that prints the values of an array of numbers and an array of strings using the Dumper function. An array of five numbers and an array of four string values have been define in the script. The values of these arrays have been printed later.

Output:

The following output appears after executing the script. According to the output, the values of the array of numbers are printed as number values, and the values of the array of strings are printed as string values:

Example 3: Using the Data::Dumper for the Hash Variable

Create a Perl file with the following script that prints the values of a hash variable using the Dumper function. A hash variable of four key-value pairs is declared in the script. The keys and values of this hash variable are printed later:

Output:

The following output appears after executing the script. According to the output, four key-value pairs of the hash variable are printed by the $VAR1 Dumper variable:

Example 4: Using the Data::Dumper to Read the File

Create a text file named “test.txt” with some content to check the script of this example. Here, the following content is added to the “test.txt” file:

test.txt

This file is created for testing purposes.

Create a Perl file with the following script that opens the “test.txt” file for reading, read the first line of the file into a variable, and print the variable using the Dumper function. Here, the “<” operator is used to open the file for reading. The first line of the file is read using the file handler named “f_handler” and stored into the $data variable. The content of this variable is printed by the Dumper function.

Output:

The following output appears after executing the script. According to the output, the first line of the “test.txt” file is printed as a string value using the $VAR1 variable:

 

Conclusion

Some basic uses of the Dumper function are shown in the examples of this tutorial. The Perl Data::Dumper has many functionalities that can be used for various purposes which are not explained in this short tutorial. The Perl users will be able to print all the values of different types of Perl variables and it is helpful for debugging purposes.