Defensive Programming

• Syntax
  • Run perl -c myprog to check for syntax errors
• Permission
  • Must make sure of this yourself
  • On Unix, consider chmod a+rx
• Semantic
  • Make sure you pay proper attention to protocol details
  • The -w flag tells Perl to warn about various things that might be wrong
  • Place it on the hash-bang line: #! perl -w
  • CGI::Carp::carpout is a function to tell Perl where to send STDERR
  • Best way is to call carpout( \*STDOUT );
• Termination
  • The eval function traps any termination and returns the error in $@
  • Check its value after calling eval:
    if ($@) { warn "An error occurred!"; }

Review

Which of these defensive programming techniques are useful even for non-CGI Perl programs?