The only escape is

gistfile1.txt

// untested ai generated from https://stackoverflow.com/a/275295/7026063
#include <iostream>
#include <ostream>

// Conditional template
template<bool C, typename A, typename B>
struct Conditional {
    typedef A type;
};

template<typename A, typename B>
struct Conditional<false, A, B> {
    typedef B type;
};

// EnableIf template
template<bool C, typename = void>
struct EnableIf { };

template<typename Type>
struct EnableIf<true, Type> {
    typedef Type type;
};

// Identity template
template<typename T>
struct Identity {
    typedef T type;
};

// TypeList template
template<typename...>
struct TypeList;

template<typename T, typename... TT>
struct TypeList<T, TT...> {
    typedef T type;
    typedef TypeList<TT...> tail;
};

template<>
struct TypeList<> { };

// GetSize template
template<typename List>
struct GetSize;

template<typename... Items>
struct GetSize<TypeList<Items...>> {
    enum { value = sizeof...(Items) };
};

// AppendItem template
template<typename NewItem, typename List>
struct AppendItem;

template<typename NewItem, typename... Items>
struct AppendItem<NewItem, TypeList<Items...>> {
    typedef TypeList<Items..., NewItem> type;
};

// PrependItem template
template<typename NewItem, typename List>
struct PrependItem;

template<typename NewItem, typename... Items>
struct PrependItem<NewItem, TypeList<Items...>> {
    typedef TypeList<NewItem, Items...> type;
};

// GetItem template
template<typename List, int N, typename = void>
struct GetItem {
    static_assert(N >= 0, "index cannot be negative");
    static_assert(GetSize<List>::value > 0, "index too high");
    typedef typename GetItem<typename List::tail, N-1>::type type;
};

template<typename List>
struct GetItem<List, 0> {
    static_assert(GetSize<List>::value > 0, "index too high");
    typedef typename List::type type;
};

// ReplaceItem template
template<typename List, int I, typename NewItem>
struct ReplaceItem {
    static_assert(I >= 0, "index cannot be negative");
    static_assert(GetSize<List>::value > 0, "index too high");
    typedef typename PrependItem<typename List::type,
                                 typename ReplaceItem<typename List::tail, I-1, NewItem>::type>
        ::type type;
};

template<typename NewItem, typename Type, typename... T>
struct ReplaceItem<TypeList<Type, T...>, 0, NewItem> {
    typedef TypeList<NewItem, T...> type;
};

// FindItem template
template<typename List, template<typename, typename...> class Matcher, typename... Keys>
struct FindItem {
    static_assert(GetSize<List>::value > 0, "Could not match any item.");
    typedef typename List::type current_type;
    typedef typename Conditional<Matcher<current_type, Keys...>::value,
                                 Identity<current_type>,
                                 FindItem<typename List::tail, Matcher, Keys...>>
        ::type::type type;
};

// Direction enum
enum Direction {
    Left = -1,
    Right = 1
};

// Rule template
template<typename OldState, typename Input, typename NewState, typename Output, Direction Move>
struct Rule {
    typedef OldState old_state;
    typedef Input input;
    typedef NewState new_state;
    typedef Output output;
    static Direction const direction = Move;
};

// IsSame template
template<typename A, typename B>
struct IsSame {
    enum { value = false };
};

template<typename A>
struct IsSame<A, A> {
    enum { value = true };
};

// Configuration template
template<typename Input, typename State, int Position>
struct Configuration {
    typedef Input input;
    typedef State state;
    enum { position = Position };
};

// Max template
template<int A, int B>
struct Max {
    enum { value = A > B ? A : B };
};

// State template
template<int n>
struct State {
    enum { value = n };
    static char const* name;
};

template<int n>
char const* State<n>::name = "unnamed";

// QAccept and QReject states
struct QAccept {
    enum { value = -1 };
    static char const* name;
};

struct QReject {
    enum { value = -2 };
    static char const* name;
};

char const* QAccept::name = "qaccept";
char const* QReject::name = "qreject";

#define DEF_STATE(ID, NAME) \
    typedef State<ID> NAME; \
    template<> char const* State<ID>::name = #NAME;

// Input template
template<int n>
struct Input {
    enum { value = n };
    static char const* name;
    template<int... I>
    struct Generate {
        typedef TypeList<Input<I>...> type;
    };
};

template<int n>
char const* Input<n>::name = "unnamed";

typedef Input<-1> InputBlank;
template<> char const* Input<-1>::name = "_";

#define DEF_INPUT(ID, NAME) \
    typedef Input<ID> NAME; \
    template<> char const* Input<ID>::name = #NAME;

// Controller template
template<typename Config, typename Transitions, typename = void>
struct Controller {
    typedef Config config;
    enum { position = config::position };
    typedef typename Conditional<
        static_cast<int>(GetSize<typename config::input>::value) <= static_cast<int>(position),
        AppendItem<InputBlank, typename config::input>,
        Identity<typename config::input>>::type::type input;
    typedef typename config::state state;
    typedef typename GetItem<input, position>::type cell;

    template<typename Item, typename State, typename Cell>
    struct Matcher {
        typedef typename Item::old_state checking_state;
        typedef typename Item::input checking_input;
        enum { value = IsSame<State, checking_state>::value &&
                       IsSame<Cell, checking_input>::value };
    };
    typedef typename FindItem<Transitions, Matcher, state, cell>::type rule;
    typedef typename ReplaceItem<input, position, typename rule::output>::type new_input;
    typedef typename rule::new_state new_state;
    typedef Configuration<new_input, new_state, Max<position + rule::direction, 0>::value> new_config;
    typedef Controller<new_config, Transitions> next_step;
    typedef typename next_step::end_config end_config;
    typedef typename next_step::end_input end_input;
    typedef typename next_step::end_state end_state;
    enum { end_position = next_step::end_position };
};

// Controller specialization for accept/reject states
template<typename Input, typename State, int Position, typename Transitions>
struct Controller<Configuration<Input, State, Position>, Transitions,
                  typename EnableIf<IsSame<State, QAccept>::value ||
                                    IsSame<State, QReject>::value>::type> {
    typedef Configuration<Input, State, Position> config;
    enum { position = config::position };
    typedef typename Conditional<
        static_cast<int>(GetSize<typename config::input>::value) <= static_cast<int>(position),
        AppendItem<InputBlank, typename config::input>,
        Identity<typename config::input>>::type::type input;
    typedef typename config::state state;
    typedef config end_config;
    typedef input end_input;
    typedef state end_state;
    enum { end_position = position };
};

// TuringMachine template
template<typename Input, typename Transitions, typename StartState>
struct TuringMachine {
    typedef Input input;
    typedef Transitions transitions;
    typedef StartState start_state;
    typedef Controller<Configuration<Input, StartState, 0>, Transitions> controller;
    typedef typename controller::end_config end_config;
    typedef typename controller::end_input end_input;
    typedef typename controller::end_state end_state;
    enum { end_position = controller::end_position };
};

// Helper to print TypeList
template<typename List>
struct PrintList {
    static void print(std::ostream& os) {
        if constexpr (GetSize<List>::value > 0) {
            os << List::type::name;
            if constexpr (GetSize<typename List::tail>::value > 0) {
                PrintList<typename List::tail>::print(os);
            }
        }
    }
};

// Define inputs for each character in the string
DEF_INPUT(1, T);
DEF_INPUT(2, h);
DEF_INPUT(3, e);
DEF_INPUT(4, _); // Space (distinct from InputBlank)
DEF_INPUT(5, o);
DEF_INPUT(6, n);
DEF_INPUT(7, l);
DEF_INPUT(8, y);
DEF_INPUT(9, s);
DEF_INPUT(10, c);
DEF_INPUT(11, a);
DEF_INPUT(12, p);
DEF_INPUT(13, f);
DEF_INPUT(14, r);
DEF_INPUT(15, m);
DEF_INPUT(16, C);
DEF_INPUT(17, plus);
DEF_INPUT(18, i);
DEF_INPUT(19, M);
DEF_INPUT(20, t);
DEF_INPUT(21, P);
DEF_INPUT(22, g);

// Define states
DEF_STATE(0, Start);
DEF_STATE(1, Write_T);
DEF_STATE(2, Write_h);
DEF_STATE(3, Write_e);
DEF_STATE(4, Write_o);
DEF_STATE(5, Write_n);
DEF_STATE(6, Write_l);
DEF_STATE(7, Write_y);
DEF_STATE(8, Write_s);
DEF_STATE(9, Write_c);
DEF_STATE(10, Write_a);
DEF_STATE(11, Write_p);
DEF_STATE(12, Write_f);
DEF_STATE(13, Write_r);
DEF_STATE(14, Write_m);
DEF_STATE(15, Write_C);
DEF_STATE(16, Write_plus1);
DEF_STATE(17, Write_plus2);
DEF_STATE(18, Write_i);
DEF_STATE(19, Write_s2);
DEF_STATE(20, Write_T2);
DEF_STATE(21, Write_e2);
DEF_STATE(22, Write_m2);
DEF_STATE(23, Write_p2);
DEF_STATE(24, Write_l2);
DEF_STATE(25, Write_a2);
DEF_STATE(26, Write_t3);
DEF_STATE(27, Write_e3);
DEF_STATE(28, Write_M);
DEF_STATE(29, Write_e4);
DEF_STATE(30, Write_t4);
DEF_STATE(31, Write_a3);
DEF_STATE(32, Write_P);
DEF_STATE(33, Write_r2);
DEF_STATE(34, Write_o2);
DEF_STATE(35, Write_g);
DEF_STATE(36, Write_r3);
DEF_STATE(37, Write_a4);
DEF_STATE(38, Write_m3);
DEF_STATE(39, Write_i2);
DEF_STATE(40, Write_n2);
DEF_STATE(41, Write_g2);

// Define transitions
typedef TypeList<
    // Write "The only escape from C++ is TemplateMetaProgramming"
    Rule<Start, InputBlank, Write_T, T, Right>,
    Rule<Write_T, InputBlank, Write_h, h, Right>,
    Rule<Write_h, InputBlank, Write_e, e, Right>,
    Rule<Write_e, InputBlank, Write_, _, Right>,
    Rule<Write_, InputBlank, Write_o, o, Right>,
    Rule<Write_o, InputBlank, Write_n, n, Right>,
    Rule<Write_n, InputBlank, Write_l, l, Right>,
    Rule<Write_l, InputBlank, Write_y, y, Right>,
    Rule<Write_y, InputBlank, Write_, _, Right>,
    Rule<Write_, InputBlank, Write_e, e, Right>, // Second 'e'
    Rule<Write_e, InputBlank, Write_s, s, Right>,
    Rule<Write_s, InputBlank, Write_c, c, Right>,
    Rule<Write_c, InputBlank, Write_a, a, Right>,
    Rule<Write_a, InputBlank, Write_p, p, Right>,
    Rule<Write_p, InputBlank, Write_e, e, Right>, // Third 'e'
    Rule<Write_e, InputBlank, Write_, _, Right>,
    Rule<Write_, InputBlank, Write_f, f, Right>,
    Rule<Write_f, InputBlank, Write_r, r, Right>,
    Rule<Write_r, InputBlank, Write_o, o, Right>, // Second 'o'
    Rule<Write_o, InputBlank, Write_m, m, Right>,
    Rule<Write_m, InputBlank, Write_, _, Right>,
    Rule<Write_, InputBlank, Write_C, C, Right>,
    Rule<Write_C, InputBlank, Write_plus1, plus, Right>,
    Rule<Write_plus1, InputBlank, Write_plus2, plus, Right>,
    Rule<Write_plus2, InputBlank, Write_, _, Right>,
    Rule<Write_, InputBlank, Write_i, i, Right>,
    Rule<Write_i, InputBlank, Write_s, s, Right>, // Second 's'
    Rule<Write_s, InputBlank, Write_, _, Right>,
    Rule<Write_, InputBlank, Write_T2, T, Right>, // Second 'T'
    Rule<Write_T2, InputBlank, Write_e2, e, Right>, // Fourth 'e'
    Rule<Write_e2, InputBlank, Write_m2, m, Right>, // Second 'm'
    Rule<Write_m2, InputBlank, Write_p2, p, Right>, // Second 'p'
    Rule<Write_p2, InputBlank, Write_l2, l, Right>, // Second 'l'
    Rule<Write_l2, InputBlank, Write_a2, a, Right>, // Third 'a'
    Rule<Write_a2, InputBlank, Write_t3, t, Right>,
    Rule<Write_t3, InputBlank, Write_e3, e, Right>, // Fifth 'e'
    Rule<Write_e3, InputBlank, Write_M, M, Right>,
    Rule<Write_M, InputBlank, Write_e4, e, Right>, // Sixth 'e'
    Rule<Write_e4, InputBlank, Write_t4, t, Right>, // Second 't'
    Rule<Write_t4, InputBlank, Write_a3, a, Right>, // Fourth 'a'
    Rule<Write_a3, InputBlank, Write_P, P, Right>,
    Rule, InputBlank, Write_r2, r, Right>, // Second 'r'
    Rule<Write_r2, InputBlank, Write_o2, o, Right>, // Third 'o'
    Rule<Write_o2, InputBlank, Write_g, g, Right>,
    Rule<Write_g, InputBlank, Write_r3, r, Right>, // Third 'r'
    Rule<Write_r3, InputBlank, Write_a4, a, Right>, // Fifth 'a'
    Rule<Write_a4, InputBlank, Write_m3, m, Right>, // Third 'm'
    Rule<Write_m3, InputBlank, Write_i2, i, Right>, // Second 'i'
    Rule<Write_i2, InputBlank, Write_n2, n, Right>, // Second 'n'
    Rule<Write_n2, InputBlank, Write_g2, g, Right>, // Second 'g'
    Rule<Write_g2, InputBlank, QAccept, InputBlank, Right>
> Rules;

// Define the Turing machine
typedef TuringMachine<TypeList<>, Rules, Start> StringWriter;

// Main function
int main() {
    // Print the final tape
    PrintList<StringWriter::end_input>::print(std::cout);
    std::cout << std::endl;

    // Verify the final state is QAccept
    static_assert(IsSame<StringWriter::end_state, QAccept>::value, "Machine did not accept");
    return 0;
}