#!/usr/bin/perl -w

#!/usr/bin/perl -w 这个-w是什么意思啊，有没有传入其他参数的，都分别是什么意思？

perl --help

Usage: perl [switches] [--] [programfile] [arguments]
  -0[octal] specify record separator (\0, if no argument)
  -a autosplit mode with -n or -p (splits $_ into @F)
  -C[number/list] enables the listed Unicode features
  -c check syntax only (runs BEGIN and CHECK blocks)
  -d[:debugger] run program under debugger
  -D[number/list] set debugging flags (argument is a bit mask or alphabets)
  -e program one line of program (several -e's allowed, omit programfile)
  -f don't do $sitelib/sitecustomize.pl at startup
  -F/pattern/ split() pattern for -a switch (//'s are optional)
  -i[extension] edit <> files in place (makes backup if extension supplied)
  -Idirectory specify @INC/#include directory (several -I's allowed)
  -l[octal] enable line ending processing, specifies line terminator
  -[mM][-]module execute "use/no module..." before executing program
  -n assume "while (<>) { ... }" loop around program
  -p assume loop like -n but print line also, like sed
  -P run program through C preprocessor before compilation
  -s enable rudimentary parsing for switches after programfile
  -S look for programfile using PATH environment variable
  -t enable tainting warnings
  -T enable tainting checks
  -u dump core after parsing program
  -U allow unsafe operations
  -v print version, subversion (includes VERY IMPORTANT perl info)
  -V[:variable] print configuration summary (or a single Config.pm variable)
-w enable many useful warnings (RECOMMENDED)
  -W enable all warnings
  -x[directory] strip off text before #!perl line and perhaps cd to directory
  -X disable all warnings