perl预定义变量

- The default input and pattern-searching space.
- Contains the subpattern from the corresponding set of parentheses in the last pattern matched.
- The string matched by the last successful pattern match.
- The string preceding whatever was matched by the last successful pattern match.
- The string following whatever was matched by the last successful pattern match.
- The last bracket matched by the last search pattern.
- Set to 1 to do multi-line matching within a string, 0 to tell Perl that it can assume that strings contain a single line, for the purpose of optimizing pattern matches. Default is 0. Use of ``$*'' is deprecated in modern perls.
- The current input line number for the last file handle from which you read (or performed a seek or tell on).
- The input record separator, newline by default.
- If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel. Default is 0.
- The output field separator for the print operator.
- The output record separator for the print operator. Ordinarily the print operator simply prints out the comma-separated fields you specify, with no trailing newline or record separator assumed.
- This is like ``$,'' except that it applies to array values interpolated into a double-quoted string (or similar interpreted string). Default is a space.
- The subscript separator for multidimensional array emulation.
- The output format for printed numbers. Use of ``$#'' is deprecated.
- The current page number of the currently selected output channel.
- The current page length (printable lines) of the currently selected output channel. Default is 60.
- The number of lines left on the page of the currently selected output channel.
- The name of the current report format for the currently selected output channel. Default is name of the filehandle.
- The name of the current top-of-page format for the currently selected output channel. Default is name of the filehandle with _TOP appended.
- The current set of characters after which a string may be broken to fill continuation fields (starting with ^) in a format. Default is " \n-", to break on whitespace or hyphens.
- What formats output to perform a form feed. Default is \f.
- The current value of the write() accumulator for format() lines.
- The status returned by the last pipe close, backtick (``) command, or system() operator.
- If used in a numeric context, yields the current value of errno, with all the usual caveats. If used in a string context, yields the corresponding system error string.
- More specific information about the last system error than that provided by $!, if available. (If not, it's just $! again, except under OS/2.)
- The Perl syntax error message from the last eval() command.
- The process number of the Perl running this script.
- The real uid of this process.
- The effective uid of this process.
- The real gid of this process.
- The effective gid of this process. If you are on a machine that supports membership in multiple groups simultaneously, gives a space separated list of groups you are in.
- Contains the name of the file containing the Perl script being executed.
- The index of the first element in an array, and of the first character in a substring. As of Perl 5, assignment to ``$['' is treated as a compiler directive, and cannot influence the behavior of any other file. Its use is discouraged.
- The version + patchlevel / 1000 of the Perl interpreter.
- The current value of the debugging flags.
- The maximum system file descriptor, ordinarily 2. System file descriptors are passed to exec()ed processes, while higher file descriptors are not.
- The current set of syntax checks enabled by use strict.
- The current value of the inplace-edit extension.
- The name of the operating system under which this copy of Perl was built, as determined during the configuration process.
- The internal variable for debugging support.
- The time at which the script began running.
- The current value of the warning switch.
- The name that the Perl binary itself was executed as, from C's argv[0].
- contains the name of the current file when reading from <>.
- The array @ARGV contains the command line arguments intended for the script.
- The array @INC contains the list of places to look for Perl scripts to be evaluated by the do EXPR, require, or use constructs.
- The hash %INC contains entries for each filename that has been included via do or require.
- The hash %ENV contains your current environment. Setting a value in ENV changes the environment for child processes.
- The hash %SIG is used to set signal handlers for various signals. Example:
-emergency memory pool