syscall

A "function" call directly to the "operating system". Many of the important subroutines and functions you use aren't direct system calls, but are built up in one or more layers above the system call level. In general, Perl programmers don't need to worry about the distinction. However, if you do happen to know which Perl functions are really syscalls, you can predict which of these will set the ($ERRNO) variable on failure. Unfortunately, beginning programmers often confusingly employ the term "system call" to mean what happens when you call the Perl system function, which actually involves many syscalls. To avoid any confusion, we nearly always use say "syscall" for something you could call indirectly via Perl's syscall function, and never for something you would call with Perl's system function.