eval {
   local $dbh->{AutoCommit} = 0;
};
$self->{_can_do_transactions} = $@ ? 0 : 1;

##</code><code>##

$self->{_can_do_transactions} = eval {
    local $dbh->{AutoCommit} = 0;
    1
};

##</code><code>##

$self->{_can_do_transactions} = eval {
    $dbh->begin_work();
    $dbh->rollback()
};

##</code><code>##

my $in_trans = eval { $dbh->begin_work() };
if (!eval {

   code_that_touches_db();

   $dbh->commit() if $in_trans;
   1
}) {
   my $msg = $@;
   eval { $dbh->rollback() } if $in_trans;
   die $msg;
}

##</code><code>##

use Sub::ScopeFinalizer qw( scope_finalizer );

{
   my $in_trans = eval { $dbh->begin_work() };
   my $pending_rollback = scope_finalizer {
      local $@;
      eval { $dbh->rollback() } if $in_trans;
   };

   code_that_touches_db();

   $pending_rollback->disable();
   $dbh->commit() if $in_trans;
}

##</code><code>##

BEGIN {
   package TransactionMaybe;

   sub begin {
      my ($class, $dbh) = @_;
      my $in_trans = eval { $dbh->begin_work() };
      return bless([$dbh, $in_trans], $class);
   }

   sub commit {
      my ($self) = @_;
      my  $dbh                       =   $self->[0];
      our $in_trans; local *in_trans = \($self->[1]);
      $dbh->commit() if $in_trans;
      $in_trans = 0;
   }

   sub DESTROY {
      my ($dbh, $in_trans) = @$self;
      local $@;
      eval { $dbh->rollback() } if $in_trans;
   }

   $INC{'TransactionMaybe.pm'} = 1;
}

{
   my $transaction = TransactionMaybe->begin($dbh);
   code_that_touches_db();
   $transaction->commit();
}