Selectively importing warnings

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

Following in Ovid's footsteps, I'm trying to remove boilerplate from my code. I'm generally happy with the result, but for warnings.

I have a module with an import method. It's only purpose is to enable strict and warnings and a few other pragmas. But, I don't want it to enable all warnings, and this is where I'm a bit stumped.

package Foo;

# lots of use statements here.
use Import::Into;

sub import {
    my $target = caller;
    'strict'->import::into($target);
    'warnings'->import::into($target, qw(FATAL utf8));
    if ($] >= 5.017011) {
        # THIS IS THE PROBLEM LINE
        'warnings'->unimport::out_of($target, 'experimental::smartmatc
+h');
    }
}
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The problem is 'warnings'->unimport::out_of($target, 'experimental::smartmatch'); turns off all warnings, not just the one I want.

unimport::out_of() is calling warnings->unimport('experimental::smartmatch'); - which I think is the same as calling no warnings 'experimental::smartmatch';. But it isn't working.

So how do enable warnings (except one) via an import sub?

update: This is Perl 5.18.1. I also fixed some formatting.

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Re: Selectively importing warnings (works)
by Anonymous Monk on Nov 16, 2013 at 00:32 UTC

I think it works :)

$ perl  import-into-warnings-notToolkit.pl
f is not init but no warning
Argument "A" isn't numeric in addition (+) at import-into-warnings-not
+Toolkit.pl line 19.
f is not a number and you're warned 0
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So whatever the deal is with experimental::smartmatch it might be a bug :)

Here are all warnings forced for comparison

$ perl  -W import-into-warnings-notToolkit.pl
Use of uninitialized value $f in concatenation (.) or string at import
+-into-warnings-notToolkit.pl line 17.
f is not init but no warning
Argument "A" isn't numeric in addition (+) at import-into-warnings-not
+Toolkit.pl line 19.
f is not a number and you're warned 0
[download]

the code

#!/usr/bin/perl --
BEGIN {
    package Fake;
    $INC{'Fake.pm'}=__FILE__;
    use Import::Into;
    sub import {
        my $target = caller;
        'strict'->import::into($target);
        'warnings'->import::into($target);
        'warnings'->unimport::out_of($target, 'uninitialized');
    }
}

package Snake;
use Fake;
my $f ;
print "f is not init but no warning $f \n";
$f = 'A';
print "f is not a number @{[  0 +  $f ]}\n";


__END__
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