Predefined Variables

Perl has a sizable set of predefined variables. These are all documented in detail in the man pages so I will only describe a few of the common ones.

$_

Default argument for many routines and syntactic structures.

$?

Status word returned from last system call. The lower bytes contain the signal upon which the program died (if any) and the upper bytes contain the exit code.

$$

Process ID of script.

$<

Real user ID of user running script.

@ARGV

Command-line arguments of script. Note that $ARGV[0] is the first actual argument, not the name of the program (as in C). The name of the script is in the variable $0.

%ENV

Associative array containing the environment variables of the calling environment.