Perl in a Nutshell, 2nd Edition

Chapter 3. The Perl Executable

The perl executable is normally installed in /usr/bin or /usr/local/bin on your machine. Some people often refer to perl as the Perl interpreter, but this isn’t strictly correct, as you’ll learn shortly.

Every Perl program must be passed through the Perl executable to be executed. The first line in many Perl programs is something like:

#!/usr/bin/perl

For Unix systems, this #! (hash-bang or shebang) line tells the shell to look for the /usr/bin/perl program and pass the rest of the file to that /usr/bin/perl for execution. Sometimes, you’ll see different pathnames to the Perl executable, such as /usr/local/bin/perl. You might see perl5 or perl6 instead of perl on sites that still depend on older versions of Perl.

Often, you’ll see command-line options tacked on the end of perl, such as the notorious -w switch, which produces warning messages. But almost all Perl programs on Unix start with some variation of #!/usr/bin/perl.

If you get a mysterious “Command not found” error on a Perl program, it’s often because the path to the Perl executable is wrong. When you download Perl programs off the Internet, copy them from one machine to another, or copy them out of a book (like this one!). The first thing you should do is make sure that the #! line points to the location of the Perl executable on your system. If you’re on a Win32 platform, where the shebang path is used only to check for Perl switches, you should make sure that you run pl2bat.bat on the ...