What Zaxo doesn't provide, is a working example. So, here is one, tailored to your snippet: 
$re = '[\w-]';
my @warnings;
{
    local $SIG{__WARN__} = sub { push @warnings, shift };
    eval {'' =~ /$re/ };
}
if($@) {
    print "error: $@\n";
} else {
    foreach my $warning (@warnings) {
        print "Got a warning: $warning";
    }
}

[download]
Alternatively, you can do your checking inside the $SIG{__WARN__} sub.

Note how you need a semicolon after some "blocks" for it to work: after the assignment of the anonymous sub to $SIG{__WARN__}, and after the eval block, at least if any statement comes right after it — which you forgot.

In reply to Re: Re: trapping -w warnings by bart
in thread trapping -w warnings by Anonymous Monk

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