Postgres hangs during VACUUM (autocommit = false)

I am having trouble with setting up a scheduled VACUUM.  Since VACUUM needs
an exclusive lock, I can never get it to run.  I am using persistant
connections from a web server and use a single module to make the
connection.  I cannot autocommit because I need transactions.

So a ps gives several similar processes:

postgres 24298  0.6  1.1  6548 2964 ?        S    14:00   0:15 postgres:
httpd epilogue [local] idle in transaction
postgres 24345  0.7  1.1  6496 2984 ?        S    14:01   0:15 postgres:
httpd epilogue [local] idle in transaction
postgres 24391  0.9  1.1  6488 2900 ?        S    14:02   0:19 postgres:
httpd epilogue [local] idle in transaction

I've tried doing a $dbh->commit() ; but that does no good.  I read all the
posts I could find on this, but is there any way for me to schedule a VACUUM
that won't hang?

Autocommit is not an option.

Thanks!

Mark
epilogue.net