use File::Find;
use vars '%CatWarnOne';

find(\&finder, 'path/to/perl/sources' );

for my $k ( sort keys %CatWarnOne ){
    print "\t$k\n";
    for my $ke ( sort keys %{$CatWarnOne{$k}} ){
        print "\t\t$k\n";
    }
}

exit;
sub finder {
    return if -d $File::Find::Name;
    return unless /\.(c|xs)$/;
    open IN, $File::Find::Name
        or warn "ERROR: Couldn't open $File::Find::name : $!"
            && return;

    while(<IN>){
        if( /Perl_warner\(/ ){
            my($key, @val);
            while( not( $key and @val ) ){
                ( $key, @val ) = /Perl_warner\(.*?packWARN\((\w+)\)[^"]+? (?:"((?:[^"]|\\")+?)"[^";]*?)+\);/x;
                $_ .= <IN> if not( $key and @val );
            }
            $CatWarnOne{$key}{$_}=1 for @val;
        }
    }

    close IN;
    return;
}