Security aware programming(2)

• 'use warnings' and '-w'/'-W' options:

  • configurable warnings: use warnings qw(io syntax)
  • for security: use warnings FATAL => "all"
  • use warnings is lexically scoped
  • use warnings ignores '-w' option and $^W
  • '-W' option overrides use warnings
  • use 'perl -W script' to verify coded loaded with require/use too