Thank you guys, I just figured out the way after long trial with myself from when I post this topic to right now without any break:

foreach (keys %$reg) {
    no strict 'refs';
    my $regkey = $_ or next;
    my $regval = $reg->{$regkey} or next;
    my $sub = sub {
        return 1 if shift =~ /$regval/;
    };
    *{'is_'.$regkey} = $sub;
}

our @EXPORT = do {
    no strict 'refs';
    my @list;
    foreach (keys %Str::) {
        eval {my $sub = *$_{CODE};};
        push @list, $_ if !$@;
    }
    @list;
};
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I did not need AUTOLOAD at all. Thank you again, I'm going to read your answers from now!