What is the best way to handle exceptions in Perl?

user_86837 0
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I've noticed that Exception.pm and Error.pm don't seem to be extensively used in the Perl community. Is that due to the large footprint of eval for exception handling?

Also Perl programs appear to have a much more lenient policy regarding exception handling in general. Is there a compelling reason for this?

In any event what would be the best method for exception handling in Perl?

error-handling exception-handling perl eval
3 Answers

Never test $@ as is, because it is a global variable, so even the test itself can change it.

General eval-template:

my $result;

eval {
    $result= something();
    # ...
    1;  # ok
} or do {
    my $eval_error= $@ || "error";
    # ...
    die $eval_error;
};  # needs a semicolon

In practice that is the lightest way. It still leaves a tiny room for funny $@ behaviour, but nothing that really concerned me enough.

Admin1

As it has been mentioned you can use the traditional way with eval, but if you want to use more elaborate exception trapping, including with exception objects, then I recommend using the try-catch-finally blocks. There are quite a few perl modules that provide it such as Nice::Try and Syntax::Keyword::Try, but Syntax::Keyword::Try does not provide exception variable assignment or exception class catch like

  try
  {
    # something
  }
  catch( Exception $e )
  {
    # catch this in $e
  }

Full disclosure: I am the developer of Nice::Try

user_48149710
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