perl is the scripting language mainly used for Test Automation.
Shell is UNIX scripting language used to automate the frequently required things.
Perl is a high-level, general-purpose, interpreted, dynamic programming language
A shell script is a script written for the shell, or command line interpreter, of an operating system. It is often considered a simple domain-specific programming language. Typical operations performed by shell scripts include file manipulation, program execution, and printing text.
writing a shell script is much quicker than writing the equivalent code in other programming languages. The many advantages include easy program or file selection, quick start, and interactive debugging. A shell script can be used to provide a sequencing and decision-making linkage around existing programs, and for moderately-sized scripts the absence of a compilation step is an advantage.