You are viewing the version of this documentation from Perl 5.37.11. This is a development version of Perl.



Fatal - Replace functions with equivalents which succeed or die


use Fatal qw(open close);

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

use File::Copy qw(move);
use Fatal qw(move);

move($file1, $file2); # No need to check errors!

sub juggle { . . . }


Fatal has been obsoleted by the new autodie pragma. Please use autodie in preference to Fatal. autodie supports lexical scoping, throws real exception objects, and provides much nicer error messages.

The use of :void with Fatal is discouraged.


Fatal provides a way to conveniently replace functions which normally return a false value when they fail with equivalents which raise exceptions if they are not successful. This lets you use these functions without having to test their return values explicitly on each call. Exceptions can be caught using eval{}. See perlfunc and perlvar for details.

The do-or-die equivalents are set up simply by calling Fatal's import routine, passing it the names of the functions to be replaced. You may wrap both user-defined functions and overridable CORE operators (except exec, system, print, or any other built-in that cannot be expressed via prototypes) in this way.

If the symbol :void appears in the import list, then functions named later in that import list raise an exception only when these are called in void context--that is, when their return values are ignored. For example

use Fatal qw/:void open close/;

# properly checked, so no exception raised on error
if (not open(my $fh, '<', '/bogotic') {
    warn "Can't open /bogotic: $!";

# not checked, so error raises an exception
close FH;

The use of :void is discouraged, as it can result in exceptions not being thrown if you accidentally call a method without void context. Use autodie instead if you need to be able to disable autodying/Fatal behaviour for a small block of code.


Bad subroutine name for Fatal: %s

You've called Fatal with an argument that doesn't look like a subroutine name, nor a switch that this version of Fatal understands.

%s is not a Perl subroutine

You've asked Fatal to try and replace a subroutine which does not exist, or has not yet been defined.

%s is neither a builtin, nor a Perl subroutine

You've asked Fatal to replace a subroutine, but it's not a Perl built-in, and Fatal couldn't find it as a regular subroutine. It either doesn't exist or has not yet been defined.

Cannot make the non-overridable %s fatal

You've tried to use Fatal on a Perl built-in that can't be overridden, such as print or system, which means that Fatal can't help you, although some other modules might. See the "SEE ALSO" section of this documentation.

Internal error: %s

You've found a bug in Fatal. Please report it using the perlbug command.


Fatal clobbers the context in which a function is called and always makes it a scalar context, except when the :void tag is used. This problem does not exist in autodie.

"Used only once" warnings can be generated when autodie or Fatal is used with package filehandles (eg, FILE). It's strongly recommended you use scalar filehandles instead.


Original module by Lionel Cons (CERN).

Prototype updates by Ilya Zakharevich <>.

autodie support, bugfixes, extended diagnostics, system support, and major overhauling by Paul Fenwick <>


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


autodie for a nicer way to use lexical Fatal.

IPC::System::Simple for a similar idea for calls to system() and backticks.