but it also means that there may only be one object in the transaction.

See my example in another node in this thread about how you can easily write a wrapper package to allow this.

sub code (&) {return $_[0]}

Why not just use sub instead of code and call like transaction [ $foo, $bar ], sub { ... };?

Another small fix is that the "commit not safe after errors, transaction rolled back" message should be croak()ed, not die()d.

Not really. Note that $@ already contains the caller's filename and line number. I think this looks very nice:

died at foo.pl line 13.
commit not safe after errors, transaction rolled back at Transactions.
+pm line 123.
[download]

I wanted a (&) prototype to allow the sub keyword to be left out. So I tried several solutions to select a transaction capable object, $T being my most recent try.

But the more I think about it, typing sub isn't so bad. As you say, if you simply supply the dbh to transaction(), nested transactions can be supported.

I'll whip up a third version soon.

Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }