...
my $class="MHE::" . $opts->{type};
my $filename= $class) =~ s!::!/!g;
require "$filename.pm";
...

##</code><code>##

    eval "use MHE::$opts->{type} qw(sendHeartbeat); 1"
        or die "Couldn't load 'MHE::$opts->{type}': $@";