perl語言use warning命令和-w的區別

   Perl語言編程不安全語法檢查可用下面兩個命令:

#!/usr/bin/perl -w

   或者:

use warnings;

    雖然二者均可以提示不安全的語法, 可是仍是有差異的, Perl幫助文檔裏面寫到:

    The warnings pragma is a replacement for the command line flag -w, but the pragma is limited to the enclosing block, while the flag is global.

    可見前者的做用範圍是全局, 然後者可由下面語句提早終結:

no warnings;