diff --git a/build/msbuild/lol.vars.props b/build/msbuild/lol.vars.props
index d47c4ee3..e5e376de 100644
--- a/build/msbuild/lol.vars.props
+++ b/build/msbuild/lol.vars.props
@@ -5,7 +5,7 @@
     <ExternalDir>$(SolutionDir)\..\external</ExternalDir>
 
     <!-- PEGTL -->
-    <PegtlDir>$(ExternalDir)\pegtl-0.32</PegtlDir>
+    <PegtlDir>$(ExternalDir)\pegtl-1.3.1</PegtlDir>
     <PegtlIncludes>$(PegtlDir)\include</PegtlIncludes>
 
     <!-- imgui -->
diff --git a/configure.ac b/configure.ac
index b486ab08..76b35f3f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -296,7 +296,7 @@ fi
 
 dnl  Use pegtl? Yes, always
 if true; then
-  LOL_CFLAGS="$LOL_CFLAGS -I\$(top_srcdir)/external/pegtl-0.32/include"
+  LOL_CFLAGS="$LOL_CFLAGS -I\$(top_srcdir)/external/pegtl-1.3.1/include"
 fi
 
 
diff --git a/src/gpu/shader.cpp b/src/gpu/shader.cpp
index 8b01d330..cc7144f5 100644
--- a/src/gpu/shader.cpp
+++ b/src/gpu/shader.cpp
@@ -117,42 +117,22 @@ using namespace pegtl;
 
 struct lolfx_parser
 {
-public:
-    lolfx_parser(String const &code)
-      : m_section("header")
-    {
-        basic_parse_string<struct lolfx>(std::string(code.C()), this);
-    }
-
 public:
     String m_section;
     map<String, String> m_programs;
 
 private:
-    struct do_title : action_base<do_title>
-    {
-        static void apply(std::string const &ctx, lolfx_parser *that)
-        {
-            that->m_section = ctx.c_str();
-        }
-    };
-
-    struct do_code : action_base<do_code>
-    {
-        static void apply(std::string const &ctx, lolfx_parser *that)
-        {
-            that->m_programs[that->m_section] = ctx.c_str();
-        }
-    };
-
     // title <- '[' (!']')+ ']' .{eol}
+    struct do_title
+      : plus<not_one<']'>> {};
+
     struct title
       : seq<one<'['>,
-            ifapply<plus<not_one<']'>>, do_title>,
+            do_title,
             one<']'>,
             until<eol, any>> {};
 
-    // FIXME: I’m using this rule because the ifapply<> above also
+    // FIXME: I’m using this rule because the do_title above also
     // gets triggered when using at<> which is non-consuming.
     struct title_ignore
       : seq<one<'['>,
@@ -166,7 +146,7 @@ private:
 
     // code_section < code_line{&(title / eof)}
     struct code_section
-      : ifapply<until<at<sor<title_ignore, pegtl::eof>>, code_line>, do_code> {};
+      : until<at<sor<title_ignore, pegtl::eof>>, code_line> {};
 
     // shader < title code_section
     struct shader
@@ -179,6 +159,35 @@ private:
     // lolfx < header code_section*
     struct lolfx
       : seq<header, star<shader>> {};
+
+    // default action: nothing
+    template<typename RULE>
+    struct action : nothing<RULE> {};
+
+public:
+    lolfx_parser(String const &code)
+      : m_section("header")
+    {
+        pegtl::parse<lolfx, action>(code.C(), "shader", this);
+    }
+};
+
+template<>
+struct lolfx_parser::action<lolfx_parser::do_title>
+{
+    static void apply(input const &in, lolfx_parser *that)
+    {
+        that->m_section = in.string().c_str();
+    }
+};
+
+template<>
+struct lolfx_parser::action<lolfx_parser::code_section>
+{
+    static void apply(input const &in, lolfx_parser *that)
+    {
+        that->m_programs[that->m_section] = in.string().c_str();
+    }
 };
 
 /*
diff --git a/tools/lolremez/expression.h b/tools/lolremez/expression.h
index 5198880a..fac9782d 100644
--- a/tools/lolremez/expression.h
+++ b/tools/lolremez/expression.h
@@ -28,7 +28,7 @@ namespace grammar
 
 using namespace pegtl;
 
-enum class op : uint8_t
+enum class id : uint8_t
 {
     /* Variables and constants */
     x,
@@ -46,45 +46,8 @@ enum class op : uint8_t
     min, max,
 };
 
-// Map operation enums to pegl::string<> rules
-template<op OP> struct r_call_string {};
-
-template<> struct r_call_string<op::abs>   : string<'a','b','s'> {};
-template<> struct r_call_string<op::sqrt>  : string<'s','q','r','t'> {};
-template<> struct r_call_string<op::cbrt>  : string<'c','b','r','t'> {};
-template<> struct r_call_string<op::exp>   : string<'e','x','p'> {};
-template<> struct r_call_string<op::exp2>  : string<'e','x','p','2'> {};
-template<> struct r_call_string<op::log>   : string<'l','o','g'> {};
-template<> struct r_call_string<op::log2>  : string<'l','o','g','2'> {};
-template<> struct r_call_string<op::log10> : string<'l','o','g','1','0'> {};
-template<> struct r_call_string<op::sin>   : string<'s','i','n'> {};
-template<> struct r_call_string<op::cos>   : string<'c','o','s'> {};
-template<> struct r_call_string<op::tan>   : string<'t','a','n'> {};
-template<> struct r_call_string<op::asin>  : string<'a','s','i','n'> {};
-template<> struct r_call_string<op::acos>  : string<'a','c','o','s'> {};
-template<> struct r_call_string<op::atan>  : string<'a','t','a','n'> {};
-template<> struct r_call_string<op::sinh>  : string<'s','i','n','h'> {};
-template<> struct r_call_string<op::cosh>  : string<'c','o','s','h'> {};
-template<> struct r_call_string<op::tanh>  : string<'t','a','n','h'> {};
-
-template<> struct r_call_string<op::atan2> : string<'a','t','a','n','2'> {};
-template<> struct r_call_string<op::pow>   : string<'p','o','w'> {};
-template<> struct r_call_string<op::min>   : string<'m','i','n'> {};
-template<> struct r_call_string<op::max>   : string<'m','a','x'> {};
-
 struct expression
 {
-    /*
-     * Parse arithmetic expression in x, e.g. 2*x+3
-     */
-    void parse(std::string const &str)
-    {
-        m_ops.empty();
-        m_constants.empty();
-
-        basic_parse_string<r_stmt>(str, this);
-    }
-
     /*
      * Evaluate expression at x
      */
@@ -96,12 +59,12 @@ struct expression
         for (int i = 0; i < m_ops.count(); ++i)
         {
             /* Rules that do not consume stack elements */
-            if (m_ops[i].m1 == op::x)
+            if (m_ops[i].m1 == id::x)
             {
                 stack.push(x);
                 continue;
             }
-            else if (m_ops[i].m1 == op::constant)
+            else if (m_ops[i].m1 == id::constant)
             {
                 stack.push(m_constants[m_ops[i].m2]);
                 continue;
@@ -112,39 +75,39 @@ struct expression
 
             switch (m_ops[i].m1)
             {
-            case op::plus:  stack.push(head);  break;
-            case op::minus: stack.push(-head); break;
-
-            case op::abs:   stack.push(fabs(head));  break;
-            case op::sqrt:  stack.push(sqrt(head));  break;
-            case op::cbrt:  stack.push(cbrt(head));  break;
-            case op::exp:   stack.push(exp(head));   break;
-            case op::exp2:  stack.push(exp2(head));  break;
-            case op::log:   stack.push(log(head));   break;
-            case op::log2:  stack.push(log2(head));  break;
-            case op::log10: stack.push(log10(head)); break;
-            case op::sin:   stack.push(sin(head));   break;
-            case op::cos:   stack.push(cos(head));   break;
-            case op::tan:   stack.push(tan(head));   break;
-            case op::asin:  stack.push(asin(head));  break;
-            case op::acos:  stack.push(acos(head));  break;
-            case op::atan:  stack.push(atan(head));  break;
-            case op::sinh:  stack.push(sinh(head));  break;
-            case op::cosh:  stack.push(cosh(head));  break;
-            case op::tanh:  stack.push(tanh(head));  break;
-
-            case op::add:   stack.push(stack.pop() + head); break;
-            case op::sub:   stack.push(stack.pop() - head); break;
-            case op::mul:   stack.push(stack.pop() * head); break;
-            case op::div:   stack.push(stack.pop() / head); break;
-
-            case op::atan2: stack.push(atan2(stack.pop(), head)); break;
-            case op::pow:   stack.push(pow(stack.pop(), head));   break;
-            case op::min:   stack.push(min(stack.pop(), head));   break;
-            case op::max:   stack.push(max(stack.pop(), head));   break;
-
-            case op::x:
-            case op::constant:
+            case id::plus:  stack.push(head);  break;
+            case id::minus: stack.push(-head); break;
+
+            case id::abs:   stack.push(fabs(head));  break;
+            case id::sqrt:  stack.push(sqrt(head));  break;
+            case id::cbrt:  stack.push(cbrt(head));  break;
+            case id::exp:   stack.push(exp(head));   break;
+            case id::exp2:  stack.push(exp2(head));  break;
+            case id::log:   stack.push(log(head));   break;
+            case id::log2:  stack.push(log2(head));  break;
+            case id::log10: stack.push(log10(head)); break;
+            case id::sin:   stack.push(sin(head));   break;
+            case id::cos:   stack.push(cos(head));   break;
+            case id::tan:   stack.push(tan(head));   break;
+            case id::asin:  stack.push(asin(head));  break;
+            case id::acos:  stack.push(acos(head));  break;
+            case id::atan:  stack.push(atan(head));  break;
+            case id::sinh:  stack.push(sinh(head));  break;
+            case id::cosh:  stack.push(cosh(head));  break;
+            case id::tanh:  stack.push(tanh(head));  break;
+
+            case id::add:   stack.push(stack.pop() + head); break;
+            case id::sub:   stack.push(stack.pop() - head); break;
+            case id::mul:   stack.push(stack.pop() * head); break;
+            case id::div:   stack.push(stack.pop() / head); break;
+
+            case id::atan2: stack.push(atan2(stack.pop(), head)); break;
+            case id::pow:   stack.push(pow(stack.pop(), head));   break;
+            case id::min:   stack.push(min(stack.pop(), head));   break;
+            case id::max:   stack.push(max(stack.pop(), head));   break;
+
+            case id::x:
+            case id::constant:
                 /* Already handled above */
                 break;
             }
@@ -155,101 +118,70 @@ struct expression
     }
 
 private:
-    lol::array<op, int> m_ops;
+    lol::array<id, int> m_ops;
     lol::array<lol::real> m_constants;
 
 private:
-    struct do_constant : action_base<do_constant>
-    {
-        static void apply(std::string const &ctx, expression *that)
-        {
-            /* FIXME: check if the constant is already in the list */
-            that->m_ops.push(op::constant, that->m_constants.count());
-            that->m_constants.push(lol::real(ctx.c_str()));
-        }
-    };
-
-    template<op OP>
-    struct do_op : action_base<do_op<OP>>
-    {
-        static void apply(std::string const &ctx, expression *that)
-        {
-            UNUSED(ctx);
-            that->m_ops.push(OP, -1);
-        }
-    };
-
     struct r_expr;
 
     // r_ <- <blank> *
     struct _ : star<space> {};
 
-    // r_call_unary <- <unary_op> "(" r_expr ")"
-    template<op OP>
-    struct r_call_unary : ifapply<seq<r_call_string<OP>,
-                                      _,
-                                      one<'('>,
-                                      _,
-                                      r_expr,
-                                      _,
-                                      one<')'>>,
-                                  do_op<OP>> {};
-
-    // r_call_binary <- <binary_op> "(" r_expr "," r_expr ")"
-    template<op OP>
-    struct r_call_binary : ifapply<seq<r_call_string<OP>,
-                                       _,
-                                       one<'('>,
-                                       _,
-                                       r_expr,
-                                       _,
-                                       one<','>,
-                                       _,
-                                       r_expr,
-                                       _,
-                                       one<')'>>,
-                                   do_op<OP>> {};
-
     // r_constant <- <digit> + ( "." <digit> * ) ? ( [eE] [+-] ? <digit> + ) ?
-    struct r_constant : ifapply<seq<plus<digit>,
-                                    opt<seq<one<'.'>,
-                                            star<digit>>>,
-                                    opt<seq<one<'e', 'E'>,
-                                            opt<one<'+', '-'>>,
-                                            plus<digit>>>>,
-                                do_constant> {};
+    struct r_constant : seq<plus<digit>,
+                            opt<seq<one<'.'>,
+                                    star<digit>>>,
+                            opt<seq<one<'e', 'E'>,
+                                    opt<one<'+', '-'>>,
+                                    plus<digit>>>> {};
 
     // r_var <- "x"
-    struct r_var : ifapply<one<'x'>, do_op<op::x>> {};
-
-    // r_call <- r_call_unary / r_call_binary
-    struct r_call : sor<r_call_unary<op::abs>,
-                        r_call_unary<op::sqrt>,
-                        r_call_unary<op::cbrt>,
-                        r_call_unary<op::exp>,
-                        r_call_unary<op::exp2>,
-                        r_call_unary<op::log>,
-                        r_call_unary<op::log2>,
-                        r_call_unary<op::log10>,
-                        r_call_unary<op::sin>,
-                        r_call_unary<op::cos>,
-                        r_call_unary<op::tan>,
-                        r_call_unary<op::asin>,
-                        r_call_unary<op::acos>,
-                        r_call_unary<op::atan>,
-                        r_call_unary<op::sinh>,
-                        r_call_unary<op::cosh>,
-                        r_call_unary<op::tanh>,
-                        r_call_binary<op::atan2>,
-                        r_call_binary<op::pow>,
-                        r_call_binary<op::min>,
-                        r_call_binary<op::max>> {};
+    struct r_var : pegtl_string_t("x") {};
+
+    // r_binary_call <- <r_binary_fun> "(" r_expr "," r_expr ")"
+    struct r_binary_fun : sor<pegtl_string_t("atan2"),
+                              pegtl_string_t("pow"),
+                              pegtl_string_t("min"),
+                              pegtl_string_t("max")> {};
+
+    struct r_binary_call : seq<r_binary_fun,
+                               _, one<'('>,
+                               _, r_expr,
+                               _, one<','>,
+                               _, r_expr,
+                               _, one<')'>> {};
+
+    // r_unary_call <- <r_unary_fun> "(" r_expr ")"
+    struct r_unary_fun : sor<pegtl_string_t("abs"),
+                             pegtl_string_t("sqrt"),
+                             pegtl_string_t("cbrt"),
+                             pegtl_string_t("exp"),
+                             pegtl_string_t("exp2"),
+                             pegtl_string_t("log"),
+                             pegtl_string_t("log2"),
+                             pegtl_string_t("log10"),
+                             pegtl_string_t("sin"),
+                             pegtl_string_t("cos"),
+                             pegtl_string_t("tan"),
+                             pegtl_string_t("asin"),
+                             pegtl_string_t("acos"),
+                             pegtl_string_t("atan"),
+                             pegtl_string_t("sinh"),
+                             pegtl_string_t("cosh"),
+                             pegtl_string_t("tanh")> {};
+
+    struct r_unary_call : seq<r_unary_fun,
+                              _, one<'('>,
+                              _, r_expr,
+                              _, one<')'>> {};
+
+    // r_call <- r_binary_call / r_unary_call
+    struct r_call : sor<r_binary_call,
+                        r_unary_call> {};
 
     // r_parentheses <- "(" r_expr ")"
     struct r_parentheses : seq<one<'('>,
-                               _,
-                               r_expr,
-                               _,
+                               pad<r_expr, space>,
                                one<')'>> {};
 
     // r_terminal <- r_call / r_var / r_constant / r_parentheses
@@ -259,16 +191,16 @@ private:
                             r_parentheses> {};
 
     // r_signed <- "-" r_signed / "+" r_signed / r_terminal
-    struct r_signed : sor<ifapply<seq<one<'-'>, _, r_signed>,
-                                  do_op<op::minus>>,
+    struct r_signed;
+    struct r_minus : seq<one<'-'>, _, r_signed> {};
+    struct r_signed : sor<r_minus,
                           seq<one<'+'>, _, r_signed>,
                           r_terminal> {};
 
     // r_exponent <- ( "^" / "**" ) r_signed
-    struct r_exponent : ifapply<seq<_,
-                                    sor<one<'^'>, string<'*', '*'>>,
-                                    _,
-                                    r_signed>, do_op<op::pow>> {};
+    struct r_exponent : seq<pad<sor<one<'^'>,
+                                    string<'*', '*'>>, space>,
+                            r_signed> {};
 
     // r_factor <- r_signed ( r_exponent ) *
     struct r_factor : seq<r_signed,
@@ -277,21 +209,138 @@ private:
     // r_mul <- "*" r_factor
     // r_div <- "/" r_factor
     // r_term <- r_factor ( r_mul / r_div ) *
-    struct r_mul : ifapply<seq<_, one<'*'>, _, r_factor>, do_op<op::mul>> {};
-    struct r_div : ifapply<seq<_, one<'/'>, _, r_factor>, do_op<op::div>> {};
+    struct r_mul : seq<_, one<'*'>, _, r_factor> {};
+    struct r_div : seq<_, one<'/'>, _, r_factor> {};
     struct r_term : seq<r_factor,
                         star<sor<r_mul, r_div>>> {};
 
     // r_add <- "+" r_term
     // r_sub <- "-" r_term
     // r_expr <- r_term ( r_add / r_sub ) *
-    struct r_add : ifapply<seq<_, one<'+'>, _, r_term>, do_op<op::add>> {};
-    struct r_sub : ifapply<seq<_, one<'-'>, _, r_term>, do_op<op::sub>> {};
+    struct r_add : seq<_, one<'+'>, _, r_term> {};
+    struct r_sub : seq<_, one<'-'>, _, r_term> {};
     struct r_expr : seq<r_term,
                         star<sor<r_add, r_sub>>> {};
 
     // r_stmt <- r_expr <end>
-    struct r_stmt : seq<_, r_expr, _, pegtl::eof> {};
+    struct r_stmt : must<pad<r_expr, space>, pegtl::eof> {};
+
+    //
+    // Default actions
+    //
+
+    template<typename R>
+    struct action : nothing<R> {};
+
+    template<id OP>
+    struct generic_action
+    {
+        static void apply(input const &in, expression *that)
+        {
+            UNUSED(in);
+            that->m_ops.push(OP, -1);
+        }
+    };
+
+public:
+    /*
+     * Parse arithmetic expression in x, e.g. 2*x+3
+     */
+    void parse(std::string const &str)
+    {
+        m_ops.empty();
+        m_constants.empty();
+
+        pegtl::parse<r_stmt, action>(str, "expression", this);
+    }
+};
+
+//
+// Rule specialisations for simple operators
+//
+
+template<> struct expression::action<expression::r_var> : generic_action<id::x> {};
+template<> struct expression::action<expression::r_exponent> : generic_action<id::pow> {};
+template<> struct expression::action<expression::r_mul> : generic_action<id::mul> {};
+template<> struct expression::action<expression::r_div> : generic_action<id::div> {};
+template<> struct expression::action<expression::r_add> : generic_action<id::add> {};
+template<> struct expression::action<expression::r_sub> : generic_action<id::sub> {};
+template<> struct expression::action<expression::r_minus> : generic_action<id::minus> {};
+
+//
+// Rule specialisations for unary and binary function calls
+//
+
+template<>
+struct expression::action<expression::r_binary_call>
+{
+    static void apply(input const &in, expression *that)
+    {
+        struct { id id; char const *name; } lut[] =
+        {
+            { id::atan2, "atan2" },
+            { id::pow,   "pow" },
+            { id::min,   "min" },
+            { id::max,   "max" },
+        };
+
+        for (auto pair : lut)
+        {
+            if (strncmp(in.string().c_str(), pair.name, strlen(pair.name)) != 0)
+                continue;
+
+            that->m_ops.push(pair.id, -1);
+            return;
+        }
+    }
+};
+
+template<>
+struct expression::action<expression::r_unary_call>
+{
+    static void apply(input const &in, expression *that)
+    {
+        struct { id id; char const *name; } lut[] =
+        {
+            { id::abs,   "abs" },
+            { id::sqrt,  "sqrt" },
+            { id::cbrt,  "cbrt" },
+            { id::exp2,  "exp2" },
+            { id::exp,   "exp" },
+            { id::log10, "log10" },
+            { id::log2,  "log2" },
+            { id::log,   "log" },
+            { id::sinh,  "sinh" },
+            { id::cosh,  "cosh" },
+            { id::tanh,  "tanh" },
+            { id::sin,   "sin" },
+            { id::cos,   "cos" },
+            { id::tan,   "tan" },
+            { id::asin,  "asin" },
+            { id::acos,  "acos" },
+            { id::atan,  "atan" },
+        };
+
+        for (auto pair : lut)
+        {
+            if (strncmp(in.string().c_str(), pair.name, strlen(pair.name)) != 0)
+                continue;
+
+            that->m_ops.push(pair.id, -1);
+            return;
+        }
+    }
+};
+
+template<>
+struct expression::action<expression::r_constant>
+{
+    static void apply(input const &in, expression *that)
+    {
+        /* FIXME: check if the constant is already in the list */
+        that->m_ops.push(id::constant, that->m_constants.count());
+        that->m_constants.push(lol::real(in.string().c_str()));
+    }
 };
 
 } /* namespace grammar */