diff --git a/src/compiler/crystal/codegen/codegen.cr b/src/compiler/crystal/codegen/codegen.cr
index 2e2610b483b6..d08b99b3dfab 100644
--- a/src/compiler/crystal/codegen/codegen.cr
+++ b/src/compiler/crystal/codegen/codegen.cr
@@ -537,7 +537,7 @@ module Crystal
                 end
                 get_global class_var_global_name(node_exp.var), node_exp.type, node_exp.var
               when Global
-                get_global node_exp.name, node_exp.type, node_exp.var
+                node.raise "BUG: there should be no use of global variables other than $~ and $?"
               when Path
                 # Make sure the constant is initialized before taking a pointer of it
                 const = node_exp.target_const.not_nil!
@@ -1017,7 +1017,7 @@ module Crystal
             when InstanceVar
               instance_var_ptr context.type, target.name, llvm_self_ptr
             when Global
-              get_global target.name, target_type, target.var
+              node.raise "BUG: there should be no use of global variables other than $~ and $?"
             when ClassVar
               read_class_var_ptr(target)
             when Var
@@ -1143,15 +1143,7 @@ module Crystal
           codegen_assign(var, value, node)
         end
       when Global
-        if value = node.value
-          request_value do
-            accept value
-          end
-
-          ptr = get_global var.name, var.type, var.var
-          assign ptr, var.type, value.type, @last
-          return false
-        end
+        node.raise "BUG: there should be no use of global variables other than $~ and $?"
       when ClassVar
         # This is the case of a class var initializer
         initialize_class_var(var)
@@ -1208,18 +1200,13 @@ module Crystal
     end
 
     def visit(node : Global)
-      read_global node.name.to_s, node.type, node.var
+      node.raise "BUG: there should be no use of global variables other than $~ and $?"
     end
 
     def visit(node : ClassVar)
       @last = read_class_var(node)
     end
 
-    def read_global(name, type, real_var)
-      @last = get_global name, type, real_var
-      @last = to_lhs @last, type
-    end
-
     def visit(node : InstanceVar)
       read_instance_var node.type, context.type, node.name, llvm_self_ptr
     end
@@ -2255,7 +2242,7 @@ module Crystal
     end
 
     def visit(node : ExpandableNode)
-      raise "BUG: #{node} at #{node.location} should have been expanded"
+      raise "BUG: #{node} (#{node.class}) at #{node.location} should have been expanded"
     end
 
     def visit(node : ASTNode)
diff --git a/src/compiler/crystal/program.cr b/src/compiler/crystal/program.cr
index 7db99a44f17b..722501add55e 100644
--- a/src/compiler/crystal/program.cr
+++ b/src/compiler/crystal/program.cr
@@ -26,10 +26,6 @@ module Crystal
     # All symbols (:foo, :bar) found in the program
     getter symbols = Set(String).new
 
-    # All global variables in the program ($foo, $bar), indexed by their name.
-    # The names includes the `$` sign.
-    getter global_vars = {} of String => MetaTypeVar
-
     # Hash that prevents recursive splat expansions. For example:
     #
     # ```
diff --git a/src/compiler/crystal/semantic/cleanup_transformer.cr b/src/compiler/crystal/semantic/cleanup_transformer.cr
index a7b48cca4fa7..864e09f7e062 100644
--- a/src/compiler/crystal/semantic/cleanup_transformer.cr
+++ b/src/compiler/crystal/semantic/cleanup_transformer.cr
@@ -265,7 +265,7 @@ module Crystal
 
       if target.is_a?(Path)
         const = target.target_const.not_nil!
-        return node unless const.used?
+        return node if !const.used? || const.cleaned_up?
 
         unless const.value.type?
           node.raise "can't infer type of constant #{const} (maybe the constant refers to itself?)"
@@ -285,6 +285,7 @@ module Crystal
       if target.is_a?(Path)
         const = const.not_nil!
         const.value = const.value.transform self
+        const.cleaned_up = true
       end
 
       if node.target == node.value
@@ -301,6 +302,18 @@ module Crystal
       node
     end
 
+    def transform(node : Path)
+      # Some constants might not have been cleaned up at this point because
+      # they don't have an explicit `Assign` node. One example is regex
+      # literals: a constant is created for them, but there's no `Assign` node.
+      if (const = node.target_const) && const.used? && !const.cleaned_up?
+        const.value = const.value.transform self
+        const.cleaned_up = true
+      end
+
+      node
+    end
+
     private def void_lib_call?(node)
       return unless node.is_a?(Call)
 
diff --git a/src/compiler/crystal/semantic/exception.cr b/src/compiler/crystal/semantic/exception.cr
index 394be93baf3f..1b367f3ddb97 100644
--- a/src/compiler/crystal/semantic/exception.cr
+++ b/src/compiler/crystal/semantic/exception.cr
@@ -314,25 +314,6 @@ module Crystal
   end
 
   class Program
-    def undefined_global_variable(node, similar_name)
-      common = String.build do |str|
-        str << "can't infer the type of global variable '#{node.name}'"
-        if similar_name
-          str << '\n'
-          str << colorize(" (did you mean #{similar_name}?)").yellow.bold.to_s
-        end
-      end
-
-      msg = String.build do |str|
-        str << common
-        str << "\n\n"
-        str << undefined_variable_message("global", node.name)
-        str << "\n\n"
-        str << common
-      end
-      node.raise msg
-    end
-
     def undefined_class_variable(node, owner, similar_name)
       common = String.build do |str|
         str << "can't infer the type of class variable '#{node.name}' of #{owner.devirtualize}"
diff --git a/src/compiler/crystal/semantic/literal_expander.cr b/src/compiler/crystal/semantic/literal_expander.cr
index c3d34946b6f1..57dd8b43e767 100644
--- a/src/compiler/crystal/semantic/literal_expander.cr
+++ b/src/compiler/crystal/semantic/literal_expander.cr
@@ -253,18 +253,16 @@ module Crystal
     #
     #     /regex/flags
     #
-    # To:
+    # To declaring a constant with this value (if not already declared):
     #
-    #     if temp_var = $some_global
-    #       temp_var
-    #     else
-    #       $some_global = Regex.new("regex", Regex::Options.new(flags))
-    #     end
+    # ```
+    # Regex.new("regex", Regex::Options.new(flags))
+    # ```
     #
-    # That is, cache the regex in a global variable.
+    # and then reading from that constant.
+    # That is, we cache regex literals to avoid recompiling them all of the time.
     #
     # Only do this for regex literals that don't contain interpolation.
-    #
     # If there's an interpolation, expand to: Regex.new(interpolation, flags)
     def expand(node : RegexLiteral)
       node_value = node.value
@@ -273,30 +271,19 @@ module Crystal
         string = node_value.value
 
         key = {string, node.options}
-        index = @regexes.index key
-        unless index
-          index = @regexes.size
-          @regexes << key
-        end
-
-        global_name = "$Regex:#{index}"
-        temp_name = @program.new_temp_var_name
+        index = @regexes.index(key) || @regexes.size
+        const_name = "$Regex:#{index}"
 
-        global_var = MetaTypeVar.new(global_name)
-        global_var.owner = @program
-        type = @program.nilable(@program.regex)
-        global_var.freeze_type = type
-        global_var.type = type
+        if index == @regexes.size
+          @regexes << key
 
-        # TODO: need to bind with nil_var for codegen, but shouldn't be needed
-        global_var.bind_to(@program.nil_var)
+          const_value = regex_new_call(node, StringLiteral.new(string).at(node))
+          const = Const.new(@program, @program, const_name, const_value)
 
-        @program.global_vars[global_name] = global_var
+          @program.types[const_name] = const
+        end
 
-        first_assign = Assign.new(Var.new(temp_name).at(node), Global.new(global_name).at(node)).at(node)
-        regex = regex_new_call(node, StringLiteral.new(string).at(node))
-        second_assign = Assign.new(Global.new(global_name).at(node), regex).at(node)
-        If.new(first_assign, Var.new(temp_name).at(node), second_assign).at(node)
+        Path.new(const_name)
       else
         regex_new_call(node, node_value)
       end
diff --git a/src/compiler/crystal/semantic/main_visitor.cr b/src/compiler/crystal/semantic/main_visitor.cr
index cf8d75a3513e..2c3f3e0c4275 100644
--- a/src/compiler/crystal/semantic/main_visitor.cr
+++ b/src/compiler/crystal/semantic/main_visitor.cr
@@ -423,22 +423,6 @@ module Crystal
         class_var = lookup_class_var(var)
         var.var = class_var
         class_var.thread_local = true if thread_local
-      when Global
-        if @untyped_def
-          node.raise "declaring the type of a global variable must be done at the class level"
-        end
-
-        thread_local = check_class_var_annotations
-        if thread_local
-          global_var = @program.global_vars[var.name]
-          global_var.thread_local = true
-        end
-
-        if value = node.value
-          type_assign(var, value, node)
-          node.bind_to(var)
-          return false
-        end
       else
         raise "Bug: unexpected var type: #{var.class}"
       end
@@ -586,39 +570,12 @@ module Crystal
         node.bind_to expanded
         node.expanded = expanded
       else
-        visit_global node
+        node.raise "BUG: there should be no use of global variables other than $~ and $?"
       end
 
       false
     end
 
-    def visit_global(node)
-      var = lookup_global_variable(node)
-
-      if first_time_accessing_meta_type_var?(var)
-        var_type = var.type?
-        if var_type && !var_type.includes_type?(program.nil)
-          node.raise "global variable '#{node.name}' is read here before it was initialized, rendering it nilable, but its type is #{var_type}"
-        end
-        var.bind_to program.nil_var
-      end
-
-      node.bind_to var
-      node.var = var
-      var
-    end
-
-    def lookup_global_variable(node)
-      var = program.global_vars[node.name]?
-      undefined_global_variable(node) unless var
-      var
-    end
-
-    def undefined_global_variable(node)
-      similar_name = lookup_similar_global_variable_name(node)
-      program.undefined_global_variable(node, similar_name)
-    end
-
     def undefined_instance_variable(owner, node)
       similar_name = lookup_similar_instance_variable_name(node, owner)
       program.undefined_instance_variable(node, owner, similar_name)
@@ -637,14 +594,6 @@ module Crystal
       end
     end
 
-    def lookup_similar_global_variable_name(node)
-      Levenshtein.find(node.name) do |finder|
-        program.global_vars.each_key do |name|
-          finder.test(name)
-        end
-      end
-    end
-
     def first_time_accessing_meta_type_var?(var)
       return false if var.uninitialized?
 
@@ -924,26 +873,7 @@ module Crystal
     end
 
     def type_assign(target : Global, value, node)
-      thread_local = check_class_var_annotations
-
-      value.accept self
-
-      var = lookup_global_variable(target)
-
-      # If we are assigning to a global inside a method, make it nilable
-      # if this is the first time we are assigning to it, because
-      # the method might be called conditionally
-      if @typed_def && first_time_accessing_meta_type_var?(var)
-        var.bind_to program.nil_var
-      end
-
-      var.thread_local = true if thread_local
-      target.var = var
-
-      target.bind_to var
-
-      node.bind_to value
-      var.bind_to value
+      node.raise "BUG: there should be no use of global variables other than $~ and $?"
     end
 
     def type_assign(target : ClassVar, value, node)
@@ -2490,7 +2420,7 @@ module Crystal
       when ClassVar
         visit_class_var exp
       when Global
-        visit_global exp
+        node.raise "BUG: there should be no use of global variables other than $~ and $?"
       when Path
         exp.accept self
         if const = exp.target_const
diff --git a/src/compiler/crystal/types.cr b/src/compiler/crystal/types.cr
index c0188f475c03..2375b4946cca 100644
--- a/src/compiler/crystal/types.cr
+++ b/src/compiler/crystal/types.cr
@@ -3152,6 +3152,9 @@ module Crystal
     property? used = false
     property? visited = false
 
+    # Was this const's value cleaned up by CleanupTransformer yet?
+    property? cleaned_up = false
+
     # Is this constant accessed with pointerof(...)?
     property? pointer_read = false