Perl warning printed without 'use warnings' or -w in any files

Question

I have a lot of old Perl code that gets called frequently, I have been writing a new module and all of a sudden I\'m getting a lot of warnings in my error_log for Apache, they a

Answer 1

I take it that the code gets called by running certain top-level Perl script(s).

Then use the __WARN__ hook in those script(s) to stop printing of warnings

BEGIN { $SIG{__WARN__} = sub {} };

Place this BEGIN block before the use statements so to affect modules as well.

An empty subroutine is the way to mute warnings since __WARN__ doesn't support 'IGNORE'.

See warn and %SIG in perlvar. See this post and this post for comments and some examples.

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To investigate further and track the warnings you can use Carp

BEGIN {
    $SIG{__WARN__} = \&Carp::cluck;  # or Carp::confess; to also die
}

which will make it print full stack traces. This can be fine-tuned as you please since we can write our own sub to be called. Or use Carp::Always.

See this post for some more drastic measures (like overriding CORE::GLOBAL::warn)

Once you find a more precise level at which to suppress warnings then local $SIG{__WARN__} is the way to go, if possible. This is used in a post linked above, and here is another example. It is of course far better to suppress warnings only where needed instead of everywhere.

More detail

• Getting stack traces in Perl?

• How can I get a call stack listing in Perl?

Note that longmess is unfortunately no longer so standard and well supported.