perl:tldr:5d647

This command is executed in the command line using Perl.

Let's break down the command:

• perl: This is the command to execute the Perl interpreter.
• -p: This flag tells Perl to loop over the input file(s) line by line, executing the script on each line.
• -i'.${extension}': This flag instructs Perl to edit the input file in-place and create a backup of the original file with an extension appended. ${extension} is a variable that holds the desired extension for the backup file. The '.${extension}' construct ensures the variable is expansion.
• -e: This flag indicates that the following string is the script to be executed.
• s/${regular_expression}/${replacement}/g: This is a regular expression substitution pattern. It tells Perl to find all occurrences of ${regular_expression} in each line of the input file and replace them with ${replacement}. The g flag stands for global, meaning all occurrences within a line should be replaced, not just the first one.
• ${filename}: This variable holds the name of the file on which the Perl script should be executed.

In summary, this command uses Perl to modify a file by replacing all occurrences of ${regular_expression} with ${replacement} in each line of ${filename}. It also creates a backup of the original file with an appended ${extension}.