duelafn has asked for the wisdom of the Perl Monks concerning the following question:

I Must have some crazy silly mistake in my code or my understanding. I don't quite get my expected output from the following very short script. 

### die.pl
#!/usr/bin/perl
use strict; use warnings;
$SIG{__DIE__} = sub { print "In die: '@_'"; };

print "Hello!\n";
die "Hi";
print "Goodbye!\n";

### Result:
[duelafn@teckla]$ ./die.pl 
Hello!
In die: 'Hi at ./die.pl line 6.
Hi at ./die.pl line 6.
'[duelafn@teckla]$

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Two things did not happen as expected. First, I expected execution to continue to print "Goodbye!\n";. Second, I don't get where the double message is coming from.

Any ideas or suggestions?

Update: Missed the inability to cheat death. Thanks! Any thoughts on the double message? - both messages appear between my single quotes!

Update 2: Nevermind, figured out the double message. Quotes are in the right place if I disable buffering $| = 1. Thanks all!

Good Day,
    Dean

Replies are listed 'Best First'.
Re: $SIG{__DIE__} not working as expected
by pc88mxer (Vicar) on Jun 09, 2008 at 00:29 UTC
    Perhaps this part of the perldoc -f die documentation explains what is going on: 
        You can arrange for a callback to be run just before the "die"
    does its deed, by setting the $SIG{__DIE__} hook. ...
    You can change the message by die-ing again in your handler, but you cannot prevent death.

    If you need to continue, wrap your code in an eval block: 

    eval {
  ...
  die "Hi!";
};
print "cheated death!\n";

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      Or just override die: 
      {
    local *CORE::GLOBAL::die = sub {
        print "Really die? ";
        if (($resp = <STDIN>) =~ /^y/i) {
            CORE::die @_;
        } else {
            print "narrowly averted: @_\n";
        }
    };
    # do the thing that dies
}

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Re: $SIG{__DIE__} not working as expected
by ferreira (Chaplain) on Jun 09, 2008 at 00:37 UTC
    Any ideas or suggestions?

    Read again the related documentation of die and $SIG{__DIE__}. In the last case, the documentation of $SGI{__DIE__} can be found at perlvar or if you have a brand new perldoc (like Pod-Perldoc-3.14_07), you can retrieve the docs that will help you with: 

    $ perldoc -v '$SIG{expr}'

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    The relevant piece is

    When a __DIE__ hook routine returns, the exception processing continues as it would have in the absence of the hook, unless the hook routine itself exits via a "goto", a loop exit, or a die().

    In other words, your current DIE handler does not stop the program from dying which explains the messages you are seeing.

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