gistfile1.txt

I added a 'print' line to the 'connect' function in my Perl 5
'perl-5.22.1/lib/site_perl/5.22.1/i686-linux-multi/DBI.pm', like so:

    sub connect {
        my $class = shift;
        my ($dsn, $user, $pass, $attr, $old_driver) = my @orig_args = @_;
        print join("--", @_), "\n";
        ⋯

And when I run this Perl 6 program:

    use Inline::Perl5;
    use DBI:from<Perl5>;

    my $dbh = DBI.connect(
        'does:not:matter',
        'dont_care',
        'dont_care',
        { some_attr => 42 }
    ) or die "Couldn't connect to database: " . DBI.errstr;

it prints:

    does:not:matter--dont_care--dont_care--some_attr--42
    DBI->connect using 'old-style' syntax is deprecated and will be an error in future versions at -e line 0.
    Can't use string ("42") as a HASH ref while "strict refs" in use at /home/perl/perlbrew/perls/perl-5.22.1/lib/site_perl/5.22.1/i686-linux-multi/DBI.pm line 607.

What happened to the attribute hash?

Just rebuilt from scratch (2017-11-22):

This is Rakudo version 2017.11-3-g0a24efc32 built on MoarVM version 2017.11
implementing Perl 6.c.

And this version of the module was just installed:

Inline::Perl5:ver<0.29>:auth<github:niner>

Same result with perl 5.26.1.

Using  ${ some_attr => 42 }  appears to solve this problem.