• exec replaces the current process with another one.
• system runs another program, wait for its completion.
• fork copies the current process; both the original and the copy continue from the same point.
• pipe sets up a pipe between two handles.
• syscall makes a low-level system call.
• eval executes (the string form will first compile) a piece of Perl code.

I know these all are system built in function to creating a process.

Uhm, you know wrongly.