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# warnings

Perl 5 version 18.2 documentation
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# warnings

- NAME
- SYNOPSIS
- DESCRIPTION

# NAME

warnings - Perl pragma to control optional warnings

# SYNOPSIS

        use warnings;    no warnings;    use warnings "all";    no warnings "all";    use warnings::register;    if (warnings::enabled()) {        warnings::warn("some warning");    }    if (warnings::enabled("void")) {        warnings::warn("void", "some warning");    }    if (warnings::enabled($object)) {        warnings::warn($object, "some warning");    }    warnings::warnif("some warning");    warnings::warnif("void", "some warning");    warnings::warnif($object, "some warning");

# DESCRIPTION

The `warnings` pragma is a replacement for the command line flag `-w` , but the pragma is limited to the enclosing block, while the flag is global. See perllexwarn for more information and the list of built-in warning categories.

If no import list is supplied, all possible warnings are either enabled or disabled.

A number of functions are provided to assist module authors.

- use warnings::register

  Creates a new warnings category with the same name as the package where the call to the pragma is used.

- warnings::enabled()

  Use the warnings category with the same name as the current package.

  Return TRUE if that warnings category is enabled in the calling module. Otherwise returns FALSE.

- warnings::enabled($category)

  Return TRUE if the warnings category, `$category` , is enabled in the calling module. Otherwise returns FALSE.

- warnings::enabled($object)

  Use the name of the class for the object reference, `$object` , as the warnings category.

  Return TRUE if that warnings category is enabled in the first scope where the object is used. Otherwise returns FALSE.

- warnings::fatal_enabled()

  Return TRUE if the warnings category with the same name as the current package has been set to FATAL in the calling module. Otherwise returns FALSE.

- warnings::fatal_enabled($category)

  Return TRUE if the warnings category `$category` has been set to FATAL in the calling module. Otherwise returns FALSE.

- warnings::fatal_enabled($object)

  Use the name of the class for the object reference, `$object` , as the warnings category.

  Return TRUE if that warnings category has been set to FATAL in the first scope where the object is used. Otherwise returns FALSE.

- warnings::warn($message)

  Print `$message` to STDERR.

  Use the warnings category with the same name as the current package.

  If that warnings category has been set to "FATAL" in the calling module then die. Otherwise return.

- warnings::warn($category, $message)

  Print `$message` to STDERR.

  If the warnings category, `$category` , has been set to "FATAL" in the calling module then die. Otherwise return.

- warnings::warn($object, $message)

  Print `$message` to STDERR.

  Use the name of the class for the object reference, `$object` , as the warnings category.

  If that warnings category has been set to "FATAL" in the scope where `$object` is first used then die. Otherwise return.

- warnings::warnif($message)

  Equivalent to:

          if (warnings::enabled())      { warnings::warn($message) }

- warnings::warnif($category, $message)

  Equivalent to:

          if (warnings::enabled($category))      { warnings::warn($category, $message) }

- warnings::warnif($object, $message)

  Equivalent to:

          if (warnings::enabled($object))      { warnings::warn($object, $message) }

- warnings::register_categories(@names)

  This registers warning categories for the given names and is primarily for use by the warnings::register pragma, for which see perllexwarn.

See Pragmatic Modules in perlmodlib and perllexwarn.

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