diff --git a/TODO.md b/TODO.md
index 51cf8e9..71e22bf 100644
--- a/TODO.md
+++ b/TODO.md
@@ -9,4 +9,4 @@
 * ✅ Implement lexer loader by file extension
 * ✅ Add --line-numbers to terminal formatter
 * Implement lexer loader by mime type
-* Implement Delegating lexers
\ No newline at end of file
+* ✅ Implement Delegating lexers
diff --git a/lexers/markdown.xml b/lexers/markdown.xml
index 058f9b6..e415ebf 100644
--- a/lexers/markdown.xml
+++ b/lexers/markdown.xml
@@ -18,19 +18,21 @@
       <rule pattern="^(\s*)([*-])(\s)(.+\n)"><bygroups><token type="TextWhitespace"/><token type="Keyword"/><token type="TextWhitespace"/><usingself state="inline"/></bygroups></rule>
       <rule pattern="^(\s*)([0-9]+\.)( .+\n)"><bygroups><token type="TextWhitespace"/><token type="Keyword"/><usingself state="inline"/></bygroups></rule>
       <rule pattern="^(\s*&gt;\s)(.+\n)"><bygroups><token type="Keyword"/><token type="GenericEmph"/></bygroups></rule>
-      <rule pattern="^(\s*```\n[\w\W]*?^\s*```$\n)"><token type="LiteralStringBacktick"/></rule>
-      <rule pattern="(?x)
-              ^(?P&lt;initial&gt;\s*```)
-              (?P&lt;lang&gt;[\w\-]+)
-              (?P&lt;afterlang&gt;
-                 (?P&lt;whitespace&gt;[^\S\n]+)
-                 (?P&lt;extra&gt;.*))?
-              (?P&lt;newline&gt;\n)
-              (?P&lt;code&gt;(.|\n)*?)
-              (?P&lt;terminator&gt;^\s*```$\n)
-              ">
-          <!-- Implement actions for delegating via a capture group -->
-         <token type="Text"/>
+      <rule pattern="^(```\n)([\w\W]*?)(^```$)">
+      <bygroups>
+        <token type="LiteralStringBacktick"/>
+        <token type="Text"/>
+        <token type="LiteralStringBacktick"/>
+      </bygroups>
+      </rule>
+      <rule pattern="^(```)(\w+)(\n)([\w\W]*?)(^```$)">
+        <bygroups>
+          <token type="LiteralStringBacktick"/>
+          <token type="NameLabel"/>  
+          <token type="TextWhitespace"/>
+          <UsingByGroup lexer="2" content="4"/>  
+          <token type="LiteralStringBacktick"/>
+        </bygroups>
       </rule>
       <rule><include state="inline"/></rule>
     </state>
diff --git a/src/actions.cr b/src/actions.cr
index 74ac190..9ae536d 100644
--- a/src/actions.cr
+++ b/src/actions.cr
@@ -16,13 +16,16 @@ module Tartrazine
     Push
     Token
     Using
+    Usingbygroup
     Usingself
   end
 
   struct Action
     property actions : Array(Action) = [] of Action
 
+    @content_index : Int32 = 0
     @depth : Int32 = 0
+    @lexer_index : Int32 = 0
     @lexer_name : String = ""
     @states : Array(String) = [] of String
     @states_to_push : Array(String) = [] of String
@@ -62,6 +65,9 @@ module Tartrazine
         @states = xml.attributes.select { |attrib|
           attrib.name == "state"
         }.map &.content
+      when ActionType::Usingbygroup
+        @lexer_index = xml["lexer"].to_i
+        @content_index = xml["content"].to_i
       end
     end
 
@@ -134,6 +140,12 @@ module Tartrazine
         tokenizer.lexer.states[new_state.name] = new_state
         tokenizer.state_stack << new_state.name
         [] of Token
+      when ActionType::Usingbygroup
+        # Shunt to content-specified lexer
+        return [] of Token if match.empty?
+        Tartrazine.lexer(String.new(match[@lexer_index].value)).tokenizer(
+          String.new(match[@content_index].value),
+          secondary: true).to_a
       else
         raise Exception.new("Unknown action type: #{@type}")
       end
diff --git a/src/lexer.cr b/src/lexer.cr
index a515baf..e38a261 100644
--- a/src/lexer.cr
+++ b/src/lexer.cr
@@ -12,24 +12,24 @@ module Tartrazine
   def self.lexer(name : String? = nil, filename : String? = nil) : BaseLexer
     return lexer_by_name(name) if name && name != "autodetect"
     return lexer_by_filename(filename) if filename
-  
+
     Lexer.from_xml(LexerFiles.get("/#{LEXERS_BY_NAME["plaintext"]}.xml").gets_to_end)
   end
-  
+
   private def self.lexer_by_name(name : String) : BaseLexer
     lexer_file_name = LEXERS_BY_NAME.fetch(name.downcase, nil)
     return create_delegating_lexer(name) if lexer_file_name.nil? && name.includes? "+"
     raise Exception.new("Unknown lexer: #{name}") if lexer_file_name.nil?
-  
+
     Lexer.from_xml(LexerFiles.get("/#{lexer_file_name}.xml").gets_to_end)
   end
-  
+
   private def self.lexer_by_filename(filename : String) : BaseLexer
     candidates = Set(String).new
     LEXERS_BY_FILENAME.each do |k, v|
       candidates += v.to_set if File.match?(k, File.basename(filename))
     end
-  
+
     case candidates.size
     when 0
       lexer_file_name = LEXERS_BY_NAME["plaintext"]
@@ -38,16 +38,17 @@ module Tartrazine
     else
       raise Exception.new("Multiple lexers match the filename: #{candidates.to_a.join(", ")}")
     end
-  
+
     Lexer.from_xml(LexerFiles.get("/#{lexer_file_name}.xml").gets_to_end)
   end
-  
+
   private def self.create_delegating_lexer(name : String) : BaseLexer
     language, root = name.split("+", 2)
     language_lexer = lexer(language)
     root_lexer = lexer(root)
     DelegatingLexer.new(language_lexer, root_lexer)
   end
+
   # Return a list of all lexers
   def self.lexers : Array(String)
     LEXERS_BY_NAME.keys.sort!