[tomminno]

vector<vector<string>> list;

for_each(list.begin(), list.end(), [](vector<string>& v)
{
    for_each(v.begin(), v.end(), [](string&s) {

    });
});

...
for(vector<string>& v : list)
{
    for(string& s : v)
    {
        ...
    }
}

//Oppure ancora meglio...
for(auto& v : list)
{
    for(auto& s : v)
    {
        ...
    }
}