3.3. Environment Variables
Environment variables are used to set
user preferences. Individual Perl modules or programs are always free
to define their own environment variables, and there is also a set of
special environment variables used in the CGI environment (see Chapter 9, "CGI Overview").
Perl uses the following environment variables:
- HOME
-
Used if chdir has no
argument.
- LOGDIR
-
Used if chdir has no argument and HOME is not
set.
- PATH
-
Used in executing subprocesses and in finding the script if
-S is used.
- PATHEXT
-
On Win32 systems, if you want to avoid typing the extension every
time you execute a Perl script, you can set the PATHEXT environment
variable so
that it includes Perl scripts. For example:
C:\> set PATHEXT=%PATHEXT%;.PLX
This setting lets you type:
C:\> myscript
without including the file extension. Be careful when setting PATHEXT
permanently—it also includes executable file types such as
.com, .exe, .bat, and
.cmd. If you inadvertently lose those
extensions, you'll have difficulty invoking
applications and script files.
- PERL5LIB
-
A colon-separated list of directories in which to look for Perl library files
before looking in the standard library and the current directory. If
PERL5LIB is not defined, PERLLIB is used. When running taint checks,
neither variable is used. The script should instead say:
use lib "/my/directory";
- PERL5OPT
-
Command-line options (switches). Switches
in this
variable are taken as if they were on every Perl command line. Only
the -[DIMUdmw] switches are
allowed. When running taint checks, this variable is ignored.
- PERLLIB
-
A colon-separated list of directories in which to look for Perl library files
before looking in the standard library and the current directory. If
PERL5LIB is defined, PERLLIB is not used.
- PERL5DB
-
The command used to load the debugger code. The default is:
BEGIN { require 'perl5db.pl' }
- PERL5SHELL
-
On Win32 systems, may be set to an alternative shell for Perl
to use
internally to execute "backtick"
commands or the system function.
- PERL_DEBUG_MSTATS
-
Relevant only if your Perl executable
was built with -DDEBUGGING_MSTATS. If set, causes memory statistics
to be dumped after execution. If set to an integer greater than 1, it
also causes memory statistics to be dumped after compilation.
- PERL_DESTRUCT_LEVEL
-
Relevant only if your Perl executable
was built with -DDEBUGGING. Controls the behavior of global
destruction of objects and other references.
Perl also has environment variables that control how Perl handles
data specific to particular natural languages. See the
perllocale manpage.
 |  |  |
| 3.2. Command-Line Options |  | 3.4. The Perl Compiler |
Copyright © 2002 O'Reilly & Associates. All rights reserved.