A.1 Command Interpretation
The Perl programs in this
book start with a line something like:#!/usr/bin/perl
On Unix (or Linux) systems, the first line of a file can include the
name of a program and some flags, which are optional. The line must
start with #!, followed by the full pathname of
the program (in this case, the Perl interpreter), followed optionally
by a single group of one or more flags. It's common
in Perl programs to see the
-w flag on this first command
interpreter line, like so: #!/usr/bin/perl -w
The -w flag turns on extra warnings. I prefer to
do that with the line:use warnings;
because it's more portable to different operating
systems.If the Perl program file is called myprogram and
has executable permissions, you can type myprogram
(or possibly ./myprogram or the full or relative
pathname for the program) to start the program running.The Unix operating system starts the program specified in the command
interpretation line and gives it as input the rest of the file after
the first line. So, in this case, it starts the Perl interpreter and
gives it the program in the file to run.This is just a shortcut for typing the following at the command line:/usr/bin/perl myprogram
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