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The syscall calls a system function, This function is passed a list as follows the first element of the list contains the name of a program to execute and the other elements are arguments to be passed to the program This function is passed a list as follows the first element of the list contains the name of a program to execute and the other elements are arguments to be passed to the program. The exec function is simular to the system function, except that it terminates the current program befre starting a new one. It provides a way for the child and parent process to communicate. The pipe function is designed to be used in conjunction with the fork function. your child process might wind up executing code that your parent process is supposed to execute, or vice versa.if you use fork in a loop, the program might wind up generating many copies of itself.if both copies of the program execute calls to print or any other output-generating function, the output from one copy might be mixed with the output from the other copy.Fork returnes zero to the child process and a non-zero value to the parent process, this non-zero value is the process ID of the child process. The fork function creates two copies of your program, the parent process and the child process. When system is called it starts a process that runs the program passed to it and waits until the process terminates. Eval function is best used for small programs for large programs it is better to use the system function The eval function treats a character string as an executable Perl program.

Several built-in functions provide different ways of creating process eval Functions that manipulate processes or programs but don't fit into any of the preceding categories.Functions that control the execution of a program or process.Functions that stop the current program or another process.Functions that start additional processes.Perl provides a wide range of functions that manipulate both the program currently being executed and other programs (also called processes) running on your machine, they are divided into four groups Process, String and Mathematical Functions