Normally shells are interactive. It means shell accept command from you (via keyboard) and execute them. But if you use command one by one (sequence of 'n' number of commands) , the you can store this sequence of command to text file and tell the shell to execute this text file instead of entering the commands. This is know as shell script.
Perl is a programming language developed by Larry Wall, especially designed for text processing. Though Perl is not officially an acronym but many times it is used as it stands for Practical Extraction and Report Language. It runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.
Perl is a well-established programming language that has been developed through the time and effort of countless free software programmers into an immensely powerful tool that can be used on pratically every operating system in the world. Perl started out as the "Swiss army knife" of computer languages and was used primarily by system administrators, but over time it's grown into an immensely robust language used by web-developers and programmers worldwide. It's also a great way to learn programming techniques and develop your own style of coding.
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