while ( $string =~ /(start.+?end)/gis ) {
    my $data = $1;
    $data =~ s/^.*start/start/is;
    print $data, "\n\n";
}

##</code><code>##

start
start
start
go
one
end
start
start
data
start
go
two
end

##</code><code>##

start
go
one
end

start
data
start
go
two
end