Special characters of perl and default internal variables

Special symbols of Perl

@ Array
$ X {} x is preceded by the dollar sign ($), followed by curly braces ({}), and is a hash element.
% To reference the entire hash, use the percent sign (") as the prefix. The hash name used in the previous pages is % family_name.
$! Some readable information generated by the system may also be error information
$ _ Subfunction Parameter Variable itself
@ _ Private variable of subroutine
& X call sub-function x
<> Data input. If no file name is specified, it will automatically open and close a series of files from the standard input stream for reading.

Default internal variables of Perl

$-Number of printable lines on the current page, part of the Perl format system
$! Returns the error code or string based on the context content.
$ "List Separator
$ # Default digital output format when printing numbers
$ Perl interpreter process ID
$ % Current page number of the current output channel
$ & String matching the previous format
$ (Group ID of the current process
$) Valid group ID of the current process
$ * Setting 1 indicates processing the multiline format. It is replaced by the/s and/m modifiers.
$, Delimiter of the current output field
$. Current row number of the last Read File
$/Delimiter of the current input record. The default value is a new line.
$: Character setting. Subsequent strings are separated to fill continuous fields.
$; Delimiter used to simulate multi-dimensional arrays.
$? Returns the status of the last external command.
$ @ Error message returned by the Perl interpreter from the eval statement
$ [Index number of the first element in the array
$ \ Delimiter of the current output record
$] Sub-version number of the Perl interpreter
$ ^ Name of the top page output format of the current channel
$ ^ A variables used to save formatted data before printing
$ ^ Value of the d test mark
$ ^ E Operating System Extension error message in non-UNIX environment
$ ^ F maximum file bundle operator Value
$ ^ H check status of the syntax activated by the compiler
$ ^ I built-in control editor Value
$ ^ L form feed sent to the output channel
$ ^ M backup memory pool size
$ ^ O operating system name
$ ^ P specifies the internal variable of the current debugging Value
$ ^ R result of the last evaluation of the regular expression Block
$ ^ S current interpreter status
$ ^ T start from the new century, and the start time of the notebook is calculated in seconds.
$ ^ W current value of the warning Switch
$ ^ X Perl binary executable code name
$ _ Default input/output and format matching space
$ | Controls the buffer of the currently selected output file handle
$ ~ Name of the current report format
$ 'String before matching information in the previous format
$ 'String after matching information in the previous format
$ + The last parenthesis matching the previous regular expression search format
$ <Real id of the user currently executing the interpreter
$ <Digits> contains parentheses corresponding to the previous regular expression.
$ = Number of printable rows on the current page
$> Valid user ID of the current process
File name containing the script being executed
$ ARGV current file name when reading from the default file handle
% ENV Environment Variable list
% INC list of files contained through do or require
% SIG signal list and Processing Method
@ _ List of parameters passed to the subroutine
@ ARGV: List of command line parameters passed to the script
@ INC: List of directories to be searched during module Import