autodie(3pm)

✨ NAME ✨

Okay so this is autodie — literally the autodie(3pm) glow-up page, bestie 💅. It swaps out functions that normally just return false when they fail for equivalents that throw an exception instead. The whole vibe is “why silently fail when you could dramatically die?” 🎀

🌸 SYNOPSIS 🌸

use autodie;            # Recommended: implies 'use autodie qw(:default)'

use autodie qw(:all);   # Recommended more: defaults and system/exec.

use autodie qw(open close);   # open/close succeed or die

open(my $fh, "<", $filename); # No need to check!

{
    no autodie qw(open);          # open failures won't die
    open(my $fh, "<", $filename); # Could fail silently!
    no autodie;                   # disable all autodies
}

print "Hello World" or die $!;    # autodie DOESN'T check print!

🦋 DESCRIPTION 🦋

bIlujDI' yIchegh()Qo'; yIHegh()!

It is better to die() than to return() in failure. -- Klingon programming proverb.

The autodie pragma is your little convenience gremlin 🧚: it replaces functions that normally return false on failure with equivalents that throw an exception on failure.

And the important part, bestie: autodie has lexical scope 👑. That means functions and subroutines altered with autodie only change their behaviour until the end of the enclosing block, file, or eval. It does not just run around changing everything forever — it knows its lane.

If system is specified as an argument to autodie, then it uses IPC::System::Simple to do the heavy lifting. See the description of that module for more information.

💖 EXCEPTIONS 💖

Exceptions produced by the autodie pragma are members of the autodie::exception class. The preferred way to work with these exceptions under Perl 5.10 is as follows:

eval {
    use autodie;

    open(my $fh, '<', $some_file);

    my @records = <$fh>;

    # Do things with @records...

    close($fh);
};

if ($@ and $@->isa('autodie::exception')) {
    if ($@->matches('open')) { print "Error from open\n";   }
    if ($@->matches(':io' )) { print "Non-open, IO error."; }
} elsif ($@) {
    # A non-autodie exception.
}

See autodie::exception for further information on interrogating exceptions.

🎀 CATEGORIES 🎀

Autodie uses a simple set of categories to group together similar built-ins. Requesting a category type (starting with a colon) will enable autodie for all built-ins beneath that category. For example, requesting :file will enable autodie for close, fcntl, open and sysopen.

The categories are currently:

:all
    :default
        :io
            read
            seek
            sysread
            sysseek
            syswrite
            :dbm
                dbmclose
                dbmopen
            :file
                binmode
                close
                chmod
                chown
                fcntl
                flock
                ioctl
                open
                sysopen
                truncate
            :filesys
                chdir
                closedir
                opendir
                link
                mkdir
                readlink
                rename
                rmdir
                symlink
                unlink
            :ipc
                kill
                pipe
                :msg
                    msgctl
                    msgget
                    msgrcv
                    msgsnd
                :semaphore
                    semctl
                    semget
                    semop
                :shm
                    shmctl
                    shmget
                    shmread
            :socket
                accept
                bind
                connect
                getsockopt
                listen
                recv
                send
                setsockopt
                shutdown
                socketpair
        :threads
            fork
    :system
        system
        exec

Note that while the above category system is presently a strict hierarchy, this should not be assumed. Lowkey do not build your whole personality on that hierarchy staying exactly like this.

A plain use autodie implies use autodie qw(:default). Note that system and exec are not enabled by default. system requires the optional IPC::System::Simple module to be installed, and enabling system or exec will invalidate their exotic forms. See BUGS below for more details.

The syntax:

use autodie qw(:1.994);

allows the :default list from a particular version to be used. This provides the convenience of using the default methods, but the surety that no behavioral changes will occur if the autodie module is upgraded. That’s the “same defaults, no surprise plot twist” vibe ✨.

autodie can be enabled for all of Perl’s built-ins, including system and exec with:

use autodie qw(:all);

🔥 FUNCTION SPECIFIC NOTES 🔥

🖨️ print

The autodie pragma does not check calls to print. So no, bestie, print is not getting autodied here. print "Hello World" or die $!; stays exactly as it is — the synopsis already said it, and I’m saying it again because the plot twist is that there is no plot twist 💀.

🔒 flock

It is not considered an error for flock to return false if it fails due to an EWOULDBLOCK (or equivalent) condition. This means one can still use the common convention of testing the return value of flock when called with the LOCK_NB option:

use autodie;

if ( flock($fh, LOCK_EX | LOCK_NB) ) {
    # We have a lock
}

Autodying flock will generate an exception if flock returns false with any other error. So EWOULDBLOCK is like “mmkay, busy, not a crisis,” and every other error is like “🚨 hello, we have a problem.”

💻 system/exec

The system built-in is considered to have failed in the following circumstances:

• The command does not start.
• The command is killed by a signal.
• The command returns a non-zero exit value (but see below).

On success, the autodying form of system returns the exit value rather than the contents of $?.

Additional allowable exit values can be supplied as an optional first argument to autodying system:

system( [ 0, 1, 2 ], $cmd, @args);  # 0,1,2 are good exit values

autodie uses the IPC::System::Simple module to change system. See its documentation for further information.

Applying autodie to system or exec causes the exotic forms system { $cmd } @args or exec { $cmd } @args to be considered a syntax error until the end of the lexical scope. If you really need to use the exotic form, you can call CORE::system or CORE::exec instead, or use no autodie qw(system exec) before calling the exotic form.

🙈 GOTCHAS 🙈

Functions called in list context are assumed to have failed if they return an empty list, or a list consisting only of a single undef element.

Some builtins (e.g. chdir or truncate) has a call signature that cannot completely be represented with a Perl prototype. This means that some valid Perl code will be invalid under autodie. As an example:

chdir(BAREWORD);

Without autodie (and assuming BAREWORD is an open filehandle/dirhandle) this is a valid call to chdir. But under autodie, chdir will behave like it had the prototype ;$ and thus BAREWORD will be a syntax error (under use strict. Without strict, it will interpreted as a filename). So yeah — plot twist, but a real one 😭.

🚨 DIAGNOSTICS 🚨

😭 :void cannot be used with lexical scope

The :void option is supported in Fatal, but not autodie. To workaround this, autodie may be explicitly disabled until the end of the current block with no autodie. To disable autodie for only a single function (eg, open) use no autodie qw(open).

autodie performs no checking of called context to determine whether to throw an exception; the explicitness of error handling with autodie is a deliberate feature. It’s giving “I said what I said” energy.

🫶 No user hints defined for %s

You’ve insisted on hints for user-subroutines, either by pre-pending a ! to the subroutine name itself, or earlier in the list of arguments to autodie. However the subroutine in question does not have any hints available.

See also DIAGNOSTICS in Fatal.

🧚 Tips and Tricks 🧚

🌈 Importing autodie into another namespace than caller

It is possible to import autodie into a different namespace by using Import::Into. However, you have to pass a caller depth (rather than a package name) for this to work correctly. That’s the whole trick — pass the depth, not the package name, bestie ✨.

💀 BUGS 💀

Used only once warnings can be generated when autodie or Fatal is used with package filehandles (eg, FILE). Scalar filehandles are strongly recommended instead.

When using autodie or Fatal with user subroutines, the declaration of those subroutines must appear before the first use of Fatal or autodie, or have been exported from a module. Attempting to use Fatal or autodie on other user subroutines will result in a compile-time error.

Due to a bug in Perl, autodie may “lose” any format which has the same name as an autodying built-in or function.

autodie may not work correctly if used inside a file with a name that looks like a string eval, such as eval (3).

🧵 autodie and string eval

Due to the current implementation of autodie, unexpected results may be seen when used near or with the string version of eval. None of these bugs exist when using block eval.

Under Perl 5.8 only, autodie does not propagate into string eval statements, although it can be explicitly enabled inside a string eval.

Under Perl 5.10 only, using a string eval when autodie is in effect can cause the autodie behaviour to leak into the surrounding scope. This can be worked around by using a no autodie at the end of the scope to explicitly remove autodie’s effects, or by avoiding the use of string eval.

None of these bugs exist when using block eval. The use of autodie with block eval is considered good practice. Block eval is the main character here 👑; string eval is the chaotic side quest.

🐛 REPORTING BUGS

Please report bugs via the GitHub Issue Tracker at https://github.com/pjf/autodie/issues.

💌 FEEDBACK 💌

If you find this module useful, please consider rating it on metacpan at https://metacpan.org/pod/autodie.

The module author loves to hear how autodie has made your life better (or worse). Feedback can be sent to pjf@perltraining.com.au.

👑 AUTHOR 👑

Copyright 2008-2009, Paul Fenwick <pjf@perltraining.com.au>

🎀 LICENSE 🎀

This module is free software. You may distribute it under the same terms as Perl itself.

🌟 SEE ALSO 🌟

• Fatal
• autodie::exception
• autodie::hints
• IPC::System::Simple

Perl tips, autodie at http://perltraining.com.au/tips/2008-08-20.html

💖 ACKNOWLEDGEMENTS 💖

Okay so before we close out, we GOTTA give credit where credit is due, because this page did not translate itself into Klingon, bestie. 😭

• Mark Reed and Roland Giersig — the Klingon translators. yes, those Klingon translators. tlhIngan Hol representation, we love to see it 🖖✨

And if you want the FULL cast list — like, every single person who touched this thing — go peep the AUTHORS file, no cap:

See the AUTHORS file for full credits. The latest version of this file can be found at https://github.com/pjf/autodie/tree/master/AUTHORS .

That URL is literally the freshest copy of the credits file, so if you're like "wait, who did this part?" — it's in there. iykyk 🫶

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And that's a wrap on autodie(3pm)! 🎀 This lil masterpiece is from perl v5.42.3, dated 2026-11-03 — yes she's serving version numbers AND a timestamp, main character energy fr fr. Go forth and use autodie; responsibly 💅🌈