Perl Special symbols and the default internal variables _perl

Special symbols for Perl

@ Array
$x {} x preceded by a dollar sign ($) followed by a curly brace ({}), it is a hash element
% to reference the entire hash, using the percent sign (") as the prefix. The hash used in the previous pages is named%family_name.
$! The system produces some readable information, or it may be an error message.
$_ the parameter variable of the child function itself
Private variable for @_ subroutine
&x Call child function X
<> data entry. If no filename is specified, it automatically opens and closes a series of files from the standard input stream to read

Perl Default Internal variables

$-the number of lines that the current page can print, part of the Perl format system
$! Returns an error number or error string based on the context content
$ "List separator
$# the default digital output format when printing numbers
$$ The process ID of the Perl interpreter
$% Current page number of the current output channel
$& a string that matches the previous format
$ (Group ID of the current process
$) Valid group ID for the current process
$* Set 1 to handle multiple-line formatting. Now replace it with the/s and/M modifiers.
$, Current output field separator
$. Current input line number of the last read file
$/current input record delimiter, default is new row
$: Character settings, subsequent strings will be separated to fill contiguous fields.
$; The delimiter to use when simulating a multidimensional array.
$? Returns the status of the previous external command
$@ The Perl interpreter returns an error message from the eval statement
The index number of the first element in the $[array
$\ the separator for the current output record
$] Sub version number of the Perl interpreter
$^ the top page output format name of the current channel
$^a variables used to save formatted data before printing
$^d the value of the debug flag
$^e operating system extended error messages in non-UNIX environments
$^f Maximum file Bundle Descriptor value
$^h the compiler-activated syntax check state
$^i the value of the built-in control editor
$^l a paper-feed break sent to the output channel
$^m the size of the standby memory pool
$^o Operating system name
$^P specifies the internal variable for the current debug value
$^r the last evaluation result of a regular expression block
$^s Current Interpreter State
$^t from the beginning of the new century, the pace of the beginning of the time calculated in seconds
The current value of the $^W warning switch
$^x perl binary Executable code name
$_ default input/output and format matching space
$| Controls the buffering of the currently selected output file handle
$~ the name of the current report format
$ ' string before matching information in the previous format
$ ' string after matching information in the previous format
$+ the last bracket that matches the last regular expression search format
$< The true ID of the user who is currently executing the interpreter
$<digits> contains the parentheses result corresponding to the last matched regular expression
$= the number of lines that the current page can print
$> A valid user ID for the current process
FileName that contains the script being executed
$ ARGV The current file name when read from the default file handle
%ENV Environment Variables List
%inc a list of files contained by do or require
%sig signal list and how to handle it
@_ a list of parameters to a subroutine
@ARGV a list of command line arguments passed to the script
@INC List of directories to search for when importing a module