[Perl] 特殊變數

$_	The default input and pattern-searching space.
$digit	Contains the subpattern from a successful parentheses pattern match.
$.	The current input line number of last filehandle read.
$!	Contains the current value of errno.
$0	The name of the file of the Perl script.
@ARGV	The command line arguments issued when the script was started.
@_	The parameter array for subroutines.
%ENV	This associative array contains your current environment.

$_ 就是「這一個變數」，也是所有迴圈會用到的預設變數。

例如要讓perl 印出1到100：

for(1..100){

print $_;

}

$1..$9 這九個特殊變數就是比對的第n個結果

$! 會顯示錯誤的訊息

ex: open(FILE, "test.txt") or die $!;

結果：

沒有此一檔案或目錄 at ./oparse.pl line 32.

若寫成 open(FILE, "test.txt") or die "$!\n";

結果：

沒有此一檔案或目錄