$dbh->{'mysql_info'}; seems to work for me, test code below, credit to kschwab for pointing this out

use strict;
use warnings;

use DBI;

my $database = 'test';

my $dsn = "DBI:mysql:$database;mysql_read_default_file=$ENV{HOME}/.my.
+cnf";
my $dbh = DBI->connect($dsn,undef,undef,{ RaiseError => 1 });

$dbh->do("update foo set bar=1");

my $info = $dbh->{'mysql_info'};

my ( $matched, $changed, $warnings ) = $info =~ /Rows matched: (\d+)  
+Changed: (\d+)  Warnings: (\d+)/;

print "Matched: $matched\nChanged: $changed\nWarnings: $warnings\n";
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