diff --git a/lib/liquid.rb b/lib/liquid.rb
index 5eda04e7..d560c792 100644
--- a/lib/liquid.rb
+++ b/lib/liquid.rb
@@ -68,6 +68,7 @@ require 'liquid/parser_switching'
 require 'liquid/tag'
 require 'liquid/tag/disabler'
 require 'liquid/tag/disableable'
+require 'liquid/parse_context'
 require 'liquid/block'
 require 'liquid/block_body'
 require 'liquid/document'
@@ -81,7 +82,6 @@ require 'liquid/standardfilters'
 require 'liquid/condition'
 require 'liquid/utils'
 require 'liquid/tokenizer'
-require 'liquid/parse_context'
 require 'liquid/partial_cache'
 require 'liquid/usage'
 require 'liquid/registers'
diff --git a/lib/liquid/block.rb b/lib/liquid/block.rb
index dc22a477..46139374 100644
--- a/lib/liquid/block.rb
+++ b/lib/liquid/block.rb
@@ -60,6 +60,21 @@ module Liquid
       @block_delimiter ||= "end#{block_name}"
     end
 
+    def self.migrate_body(start_tag_name, tokenizer, parse_context)
+      new_body, unknown_tag = BlockBody.migrate(tokenizer, parse_context)
+
+      raise SyntaxError unless unknown_tag
+
+      block_delimiter = "end#{start_tag_name}"
+      if unknown_tag.tag_name == block_delimiter
+        new_body << unknown_tag.replaced_markup("") # markup was ignored on end tags
+        return [new_body, nil]
+      end
+
+      # handle the delimiter tag in the caller
+      [new_body, unknown_tag]
+    end
+
     private
 
     # @api public
diff --git a/lib/liquid/block_body.rb b/lib/liquid/block_body.rb
index 4674c5f3..988b40d7 100644
--- a/lib/liquid/block_body.rb
+++ b/lib/liquid/block_body.rb
@@ -4,8 +4,8 @@ require 'English'
 
 module Liquid
   class BlockBody
-    LiquidTagToken      = /\A\s*(#{TagName})\s*(.*?)\z/o
-    FullToken           = /\A#{TagStart}#{WhitespaceControl}?(\s*)(#{TagName})(\s*)(.*?)#{WhitespaceControl}?#{TagEnd}\z/om
+    LiquidTagToken      = /\A\s*(#{TagName})\s*(.*?)\s*\z/o
+    FullToken           = /\A#{TagStart}#{WhitespaceControl}?(\s*)(#{TagName})(\s*)(.*?)\s*?#{WhitespaceControl}?#{TagEnd}\z/om
     ContentOfVariable   = /\A#{VariableStart}#{WhitespaceControl}?(.*?)#{WhitespaceControl}?#{VariableEnd}\z/om
     WhitespaceOrNothing = /\A\s*\z/
     TAGSTART            = "{%"
@@ -30,6 +30,16 @@ module Liquid
       end
     end
 
+    def self.migrate(tokenizer, parse_context, &block)
+      parse_context.line_number = tokenizer.line_number
+
+      if tokenizer.for_liquid_tag
+        migrate_for_liquid_tag(tokenizer, parse_context, &block)
+      else
+        migrate_for_document(tokenizer, parse_context, &block)
+      end
+    end
+
     def freeze
       @nodelist.freeze
       super
@@ -60,6 +70,56 @@ module Liquid
       yield nil, nil
     end
 
+    class UnknownTagMigrator
+      attr_reader :tag_name, :markup
+
+      def initialize(match:, markup_capture_number:, tag_name:, markup:)
+        @match = match
+        @tag_name = tag_name
+        @markup = markup
+        @markup_capture_number = markup_capture_number
+      end
+
+      def replaced_markup(new_markup)
+        Utils.match_capture_replace(@match, @markup_capture_number, new_markup)
+      end
+    end
+
+    private_class_method def self.migrate_for_liquid_tag(tokenizer, parse_context)
+      result = +""
+      while (token = tokenizer.shift)
+        if token.empty? || token.match?(WhitespaceOrNothing)
+          result << token
+          result << "\n" if tokenizer.more?
+        else
+          match = token.match(LiquidTagToken)
+          unless match
+            # Missing tag name, which was allowed in comment tags through its
+            # unknown tag handling
+            raise NotImplementedError, "TODO"
+          end
+          tag_name = match[1]
+          markup   = match[2]
+          unless (tag = Template.tags[tag_name])
+            # delegate handling of unknown tags to the caller, where a block tag may treat
+            # it as an end tag or body delimiter.
+            unknown_tag = UnknownTagMigrator.new(
+              match: match, markup_capture_number: 2, tag_name: tag_name, markup: markup
+            )
+            return [result, unknown_tag]
+          end
+          has_more_tokens = tokenizer.more?
+          new_markup, new_tag_body = tag.migrate(tag_name, markup, tokenizer, parse_context)
+          result << Utils.match_capture_replace(match, 2, new_markup)
+          result << "\n" if has_more_tokens
+          result << new_tag_body.to_s
+        end
+        parse_context.line_number = tokenizer.line_number
+      end
+
+      [result, nil]
+    end
+
     # @api private
     def self.unknown_tag_in_liquid_tag(tag, parse_context)
       Block.raise_unknown_tag(tag, 'liquid', '%}', parse_context)
@@ -109,6 +169,15 @@ module Liquid
       end
     end
 
+    private_class_method def self.migrate_liquid_tag(markup, parse_context)
+      liquid_tag_tokenizer = parse_context.new_tokenizer(
+        markup, start_line_number: parse_context.line_number, for_liquid_tag: true
+      )
+      result, unknown_tag = migrate_for_liquid_tag(liquid_tag_tokenizer, parse_context)
+      raise SyntaxError if unknown_tag
+      result
+    end
+
     private def handle_invalid_tag_token(token, parse_context)
       if token.end_with?('%}')
         yield token, token
@@ -166,6 +235,56 @@ module Liquid
       yield nil, nil
     end
 
+    private_class_method def self.migrate_for_document(tokenizer, parse_context, &block)
+      result = +""
+      while (token = tokenizer.shift)
+        next if token.empty?
+
+        case
+        when token.start_with?(TAGSTART)
+          raise SyntaxError unless token.end_with?('%}')
+          match = token.match(FullToken)
+          unless match
+            # Missing tag name, which was allowed in comment tags through its
+            # unknown tag handling
+            raise NotImplementedError, "TODO"
+          end
+          tag_name = match[2]
+          markup   = match[4]
+
+          if parse_context.line_number
+            # newlines inside the tag should increase the line number,
+            # particularly important for multiline {% liquid %} tags
+            parse_context.line_number += Regexp.last_match(1).count("\n") + Regexp.last_match(3).count("\n")
+          end
+
+          if tag_name == 'liquid'
+            new_markup = migrate_liquid_tag(markup, parse_context)
+            result << Utils.match_capture_replace(match, 4, new_markup)
+            next
+          end
+
+          unless (tag = Template.tags[tag_name])
+            # delegate handling of unknown tags to the caller, where a block tag may treat
+            # it as an end tag or body delimiter.
+            unknown_tag = UnknownTagMigrator.new(
+              match: match, markup_capture_number: 4, tag_name: tag_name, markup: markup
+            )
+            return [result, unknown_tag]
+          end
+          new_markup, new_tag_body = tag.migrate(tag_name, markup, tokenizer, parse_context)
+          result << Utils.match_capture_replace(match, 4, new_markup) << new_tag_body.to_s
+        when token.start_with?(VARSTART)
+          result << migrate_variable(token, parse_context)
+        else
+          result << token
+        end
+        parse_context.line_number = tokenizer.line_number
+      end
+
+      [result, nil]
+    end
+
     def whitespace_handler(token, parse_context)
       if token[2] == WhitespaceControl
         previous_token = @nodelist.last
@@ -246,6 +365,17 @@ module Liquid
       BlockBody.raise_missing_variable_terminator(token, parse_context)
     end
 
+    private_class_method def self.migrate_variable(token, parse_context)
+      match = token.match(ContentOfVariable)
+      if match
+        new_markup = Utils.migrate_stripped(match[1]) do |markup|
+          Variable.migrate(markup, parse_context)
+        end
+        return Utils.match_capture_replace(match, 1, new_markup)
+      end
+      BlockBody.raise_missing_variable_terminator(token, parse_context)
+    end
+
     # @deprecated Use {.raise_missing_tag_terminator} instead
     def raise_missing_tag_terminator(token, parse_context)
       BlockBody.raise_missing_tag_terminator(token, parse_context)
diff --git a/lib/liquid/document.rb b/lib/liquid/document.rb
index 7742ae5f..9b158834 100644
--- a/lib/liquid/document.rb
+++ b/lib/liquid/document.rb
@@ -28,6 +28,16 @@ module Liquid
       raise
     end
 
+    def self.migrate(tokenizer, parse_context)
+      new_body, unknown_tag = BlockBody.migrate(tokenizer, parse_context)
+      raise SyntaxError if unknown_tag
+
+      new_body
+    rescue SyntaxError => e
+      e.line_number ||= parse_context.line_number
+      raise
+    end
+
     def unknown_tag(tag, _markup, _tokenizer)
       case tag
       when 'else', 'end'
diff --git a/lib/liquid/expression.rb b/lib/liquid/expression.rb
index fcdd4d8a..f57656c5 100644
--- a/lib/liquid/expression.rb
+++ b/lib/liquid/expression.rb
@@ -41,5 +41,36 @@ module Liquid
         end
       end
     end
+
+    def self.lax_migrate(markup)
+      Utils.migrate_stripped(markup) do |markup|
+        raise ArgumentError, "unexpected empty expression" if markup.empty?
+
+        if (markup.start_with?('"') && markup.end_with?('"')) ||
+           (markup.start_with?("'") && markup.end_with?("'"))
+          markup
+        else
+          case markup
+          when INTEGERS_REGEX
+            markup
+          when RANGES_REGEX
+            match = Regexp.last_match
+            new_start, new_end = RangeLookup.lax_migrate(match[1], match[2])
+            Utils.match_captures_replace(match, 1 => new_start, 2 => new_end)
+          when FLOATS_REGEX
+            # lax parser allowed multiple periods, but the second period and following characters were ignored
+            new_markup = markup.slice(/\A(-?\d+\.\d*)/)
+            new_markup << "0" if new_markup.end_with?(".")
+            new_markup
+          else
+            if LITERALS.key?(markup)
+              markup
+            else
+              VariableLookup.lax_migrate(markup)
+            end
+          end
+        end
+      end
+    end
   end
 end
diff --git a/lib/liquid/parser_switching.rb b/lib/liquid/parser_switching.rb
index 78afd58a..a804d52c 100644
--- a/lib/liquid/parser_switching.rb
+++ b/lib/liquid/parser_switching.rb
@@ -2,6 +2,30 @@
 
 module Liquid
   module ParserSwitching
+    module ClassMethods
+      def migrate_with_selected_parser(tag_name, markup, tokenizer, parse_context)
+        case parse_context.error_mode
+        when :strict then strict_migrate(tag_name, markup, tokenizer, parse_context)
+        when :lax    then lax_migrate(tag_name, markup, tokenizer, parse_context)
+        when :warn
+          begin
+            parse_context.error_mode = :strict
+            begin
+              # Use exception side effect to conditionally branch to lax migration
+              parse(tag_name, markup, tokenizer, parse_context)
+            ensure
+              parse_context.error_mode = :warn
+            end
+
+            strict_migrate(tag_name, markup, tokenizer, parse_context)
+          rescue SyntaxError => e
+            parse_context.warnings << e
+            lax_migrate(markup)
+          end
+        end
+      end
+    end
+
     def strict_parse_with_error_mode_fallback(markup)
       strict_parse_with_error_context(markup)
     rescue SyntaxError => e
diff --git a/lib/liquid/range_lookup.rb b/lib/liquid/range_lookup.rb
index fd208a67..b76e2437 100644
--- a/lib/liquid/range_lookup.rb
+++ b/lib/liquid/range_lookup.rb
@@ -22,6 +22,37 @@ module Liquid
       end
     end
 
+    def self.lax_migrate(start_markup, end_markup)
+      new_start = Expression.lax_migrate(start_markup)
+      new_end = Expression.lax_migrate(end_markup)
+
+      # cast literals
+      start_obj = Expression.parse(new_start)
+      end_obj   = Expression.parse(new_end)
+      if start_obj.respond_to?(:evaluate) || end_obj.respond_to?(:evaluate)
+        new_start = lax_migrate_range_expression(new_start, start_obj)
+        new_end = lax_migrate_range_expression(new_end, end_obj)
+      else
+        new_start = start_obj.to_i.to_s unless start_obj.is_a?(Integer)
+        new_end = end_obj.to_i.to_s unless end_obj.is_a?(Integer)
+      end
+
+      [new_start, new_end]
+    end
+
+    def self.lax_migrate_range_expression(markup, expression)
+      return markup if expression.respond_to?(:evaluate)
+
+      case expression
+      when Integer
+        markup
+      when NilClass, String
+        expression.to_i.to_s
+      else
+        Utils.to_integer(input).to_s
+      end
+    end
+
     attr_reader :start_obj, :end_obj
 
     def initialize(start_obj, end_obj)
diff --git a/lib/liquid/tag.rb b/lib/liquid/tag.rb
index 2f7bc301..d2ada481 100644
--- a/lib/liquid/tag.rb
+++ b/lib/liquid/tag.rb
@@ -7,6 +7,8 @@ module Liquid
     include ParserSwitching
 
     class << self
+      include ParserSwitching::ClassMethods
+
       def parse(tag_name, markup, tokenizer, parse_context)
         tag = new(tag_name, markup, parse_context)
         tag.parse(tokenizer)
diff --git a/lib/liquid/tags/assign.rb b/lib/liquid/tags/assign.rb
index 7c0abd87..a877dce4 100644
--- a/lib/liquid/tags/assign.rb
+++ b/lib/liquid/tags/assign.rb
@@ -21,6 +21,18 @@ module Liquid
       raise Liquid::SyntaxError, parse_context.locale.t('errors.syntax.assign')
     end
 
+    def self.migrate(tag_name, markup, tokenizer, parse_context)
+      match = markup.match(/\s*#{Syntax}/)
+      new_variable_markup = Variable.migrate(match[2], parse_context)
+      new_markup = Utils.match_captures_replace(match, 2 => new_variable_markup)
+
+      # replace scanned over characters with a space to ensure there is a space
+      # to separate the tag name and the variable name
+      new_markup.prepend(" ") if match.begin(0) > 0
+
+      new_markup
+    end
+
     attr_reader :to, :from
 
     def initialize(tag_name, markup, parse_context)
diff --git a/lib/liquid/tags/if.rb b/lib/liquid/tags/if.rb
index d15173f8..5e176372 100644
--- a/lib/liquid/tags/if.rb
+++ b/lib/liquid/tags/if.rb
@@ -20,6 +20,39 @@ module Liquid
 
     attr_reader :blocks
 
+    def self.migrate(tag_name, markup, tokenizer, parse_context)
+      new_markup = migrate_with_selected_parser(tag_name, markup, tokenizer, parse_context)
+      new_body = migrate_body(tag_name, tokenizer, parse_context)
+      [new_markup, new_body]
+    end
+
+    def self.migrate_body(start_tag_name, tokenizer, parse_context)
+      result = +""
+
+      loop do
+        new_body, delimiter_tag = super(start_tag_name, tokenizer, parse_context)
+        result << new_body
+
+        break unless delimiter_tag
+
+        case delimiter_tag.tag_name
+        when "else"
+          result << delimiter_tag.replaced_markup("") # markup was ignored on end tags
+        when "elsif"
+          new_markup = migrate_with_selected_parser(delimiter_tag.tag_name, delimiter_tag.markup, tokenizer, parse_context)
+          result << delimiter_tag.replaced_markup(new_markup)
+        else
+          raise SyntaxError
+        end
+      end
+
+      result
+    end
+
+    private_class_method def self.strict_migrate(tag_name, markup, tokenizer, parse_context)
+      markup
+    end
+
     def initialize(tag_name, markup, options)
       super
       @blocks = []
@@ -81,6 +114,10 @@ module Liquid
       Condition.parse_expression(parse_context, markup)
     end
 
+    private_class_method def self.lax_migrate_expression(markup)
+      Expression.lax_migrate(markup)
+    end
+
     def lax_parse(markup)
       expressions = markup.scan(ExpressionsAndOperators)
       raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop =~ Syntax
@@ -101,6 +138,40 @@ module Liquid
       condition
     end
 
+    private_class_method def self.lax_migrate(tag_name, markup, tokenizer, parse_context)
+      expressions = markup.scan(ExpressionsAndOperators)
+
+      new_markup = lax_migrate_condition(expressions.pop)
+      until expressions.empty?
+        operator = expressions.pop
+        new_left_markup = lax_migrate_condition(expressions.pop)
+        new_markup = new_left_markup << operator << new_markup
+      end
+
+      new_markup
+    end
+
+    private_class_method def self.lax_migrate_condition(markup)
+      Utils.migrate_stripped(markup) do |markup|
+        match = markup.match(Syntax)
+        left = lax_migrate_expression(match[1])
+        op = match[2]
+        right_capture = match[3]
+        if op
+          right = lax_migrate_expression(right_capture) if right_capture
+        elsif right_capture
+          right = "" # remove right capture, since it is ignored with no operator
+        end
+        new_markup = Utils.match_captures_replace(match, { 1 => left, 2 => op, 3 => right }.compact)
+        new_markup.prepend(' ') if match.begin(0) > 0
+        new_markup << ' ' if match.end(0) < markup.length
+        if op && !right # missing right operand missing
+          new_markup << " nil" # replace with nil, which it was semantically treated as
+        end
+        new_markup
+      end
+    end
+
     def strict_parse(markup)
       p = Parser.new(markup)
       condition = parse_binary_comparisons(p)
diff --git a/lib/liquid/template.rb b/lib/liquid/template.rb
index 39bde833..c18fff24 100644
--- a/lib/liquid/template.rb
+++ b/lib/liquid/template.rb
@@ -96,6 +96,11 @@ module Liquid
       def parse(source, options = {})
         new.parse(source, options)
       end
+
+      def migrate(source, parse_options = {})
+        parse(source, parse_options) # raise if source has syntax errors
+        new.migrate(source, parse_options)
+      end
     end
 
     def initialize
@@ -112,6 +117,12 @@ module Liquid
       self
     end
 
+    def migrate(source, parse_options = {})
+      parse_context = configure_options(parse_options)
+      tokenizer     = parse_context.new_tokenizer(source, start_line_number: @line_numbers && 1)
+      Document.migrate(tokenizer, parse_context)
+    end
+
     def registers
       @registers ||= {}
     end
diff --git a/lib/liquid/tokenizer.rb b/lib/liquid/tokenizer.rb
index 740f8599..f03aa08c 100644
--- a/lib/liquid/tokenizer.rb
+++ b/lib/liquid/tokenizer.rb
@@ -25,6 +25,10 @@ module Liquid
       token
     end
 
+    def more?
+      @offset < @tokens.length
+    end
+
     private
 
     def tokenize
diff --git a/lib/liquid/utils.rb b/lib/liquid/utils.rb
index 38a406ef..964ed2fb 100644
--- a/lib/liquid/utils.rb
+++ b/lib/liquid/utils.rb
@@ -89,5 +89,33 @@ module Liquid
       # Otherwise return the object itself
       obj
     end
+
+    def self.migrate_stripped(markup)
+      match = markup.match(/\A\s*(.*?)\s*\z/m)
+      new_markup = yield match[1]
+      Utils.match_captures_replace(match, 1 => new_markup)
+    end
+
+    # @api private
+    def self.match_capture_replace(match, capture_number, replacement_string)
+      match_captures_replace(match, { capture_number => replacement_string })
+    end
+
+    def self.match_captures_replace(match, replacements = {})
+      new_string = match[0].dup
+      capture_numbers = replacements.keys
+      unless capture_numbers.all?(Integer)
+        raise TypeError, "Currently, only numbered captures are supported"
+      end
+      # replace from later captures first, to avoid affecting the position for following replacements
+      match_begin = match.begin(0)
+      capture_numbers.sort.reverse_each do |capture_number|
+        replacement_string = replacements.fetch(capture_number)
+        capture_start = match.begin(capture_number)
+        capture_length = match.end(capture_number) - capture_start
+        new_string[capture_start - match_begin, capture_length] = replacement_string
+      end
+      new_string
+    end
   end
 end
diff --git a/lib/liquid/variable.rb b/lib/liquid/variable.rb
index 1a4c0719..a1b06ea9 100644
--- a/lib/liquid/variable.rb
+++ b/lib/liquid/variable.rb
@@ -41,6 +41,77 @@ module Liquid
       "in \"{{#{markup}}}\""
     end
 
+    STRICT_PARSE_CONTEXT = ParseContext.new(error_mode: :strict).freeze
+    private_constant :STRICT_PARSE_CONTEXT
+
+    def self.migrate(markup, parse_context)
+      new(markup, STRICT_PARSE_CONTEXT)
+      # TODO: migrate non-integer range expression literals
+      markup
+    rescue Liquid::SyntaxError
+      raise if parse_context.error_mode == :strict
+      lax_migrate(markup, parse_context)
+    end
+
+    def self.lax_migrate(markup, parse_context)
+      # unanchored match that may skip over characters preceding the name expression
+      markup_match = markup.match(MarkupWithQuotedFragment)
+      unless markup_match
+        # Treated as a blank variable (e.g. `{{ -}}`), which outputs nothing
+        # but may still have an effect on whitespace trimming
+        return ""
+      end
+
+      name_markup = markup_match[1]
+      filters_markup = markup_match[2]
+
+      new_name_markup = Expression.lax_migrate(name_markup)
+
+      new_filter_markup = ""
+      # unanchored match that may skip over characters preceding the pipe for the first filter
+      if (filters_match = filters_markup.match(/\s*#{FilterMarkupRegex}/o))
+        filters = filters_match[1].scan(FilterParser) # may skip over unterminated quote characters
+        filters.map! do |f|
+          filter_match = f.match(/\A(\s*)\W*(\w+)(\s*)/)
+          next unless filter_match
+
+          # omit non-word characters preceding the filter name that the lax parser skips over
+          transformed_filter = +"#{filter_match[1]}#{filter_match[2]}#{filter_match[3]}"
+
+          filter_args = []
+          f.scan(/#{FilterArgsRegex}\s*/o) do # may skip over characters before the argument separator
+            filter_arg_match = Regexp.last_match
+            new_filter_arg = lax_migrate_filter_argument(filter_arg_match[1])
+            filter_arg_string = Utils.match_captures_replace(filter_arg_match, 1 => new_filter_arg)
+            filter_arg_string = filter_arg_string[1...] # remove separator character
+            filter_args << filter_arg_string
+          end
+
+          unless filter_args.empty?
+            transformed_filter << ":" << filter_args.join(",")
+          end
+
+          transformed_filter
+        end
+        filters.compact!
+        new_filters_markup = filters.join('|')
+
+        # include pipe separator along with whitespace surrounding it
+        new_filter_markup = Utils.match_captures_replace(filters_match, 1 => new_filters_markup)
+      end
+
+      Utils.match_captures_replace(markup_match, 1 => new_name_markup, 2 => new_filter_markup)
+    end
+
+    def self.lax_migrate_filter_argument(unparsed_arg)
+      if (match = unparsed_arg.match(JustTagAttributes))
+        new_value_markup = Expression.lax_migrate(match[2])
+        Utils.match_captures_replace(match, 2 => new_value_markup)
+      else
+        Expression.lax_migrate(unparsed_arg)
+      end
+    end
+
     def lax_parse(markup)
       @filters = []
       return unless markup =~ MarkupWithQuotedFragment
diff --git a/lib/liquid/variable_lookup.rb b/lib/liquid/variable_lookup.rb
index 1ade30ef..b2fec489 100644
--- a/lib/liquid/variable_lookup.rb
+++ b/lib/liquid/variable_lookup.rb
@@ -10,6 +10,41 @@ module Liquid
       new(markup)
     end
 
+    LITERALS = Expression::LITERALS.keys.freeze
+    private_constant :LITERALS
+
+    def self.lax_migrate(markup)
+      new_markup = nil
+      last_match = nil
+      first_match = nil
+      markup.scan(VariableParser) do |lookup|
+        last_match = Regexp.last_match
+        first_match ||= last_match
+        if lookup&.start_with?('[') && lookup&.end_with?(']')
+          new_markup ||= +""
+          new_markup << "[" << Expression.lax_migrate(lookup[1..-2]) << "]"
+        else
+          new_markup << "." if new_markup
+          new_markup ||= +""
+          new_markup << lookup
+        end
+      end
+
+      case new_markup
+      when nil
+        # `markup.scan(VariableParser)` may skip over all characters
+        new_markup ||= " nil "
+      when Expression::INTEGERS_REGEX, Expression::RANGES_REGEX, Expression::FLOATS_REGEX, *LITERALS
+        # Quote variable lookups that match literals after characters are skipped by regex scanning
+        new_markup = "['#{new_markup}']"
+      else
+        new_markup.prepend(" ") if first_match.begin(0) > 0
+        new_markup << ' ' if last_match.end(0) < markup.length
+      end
+
+      new_markup
+    end
+
     def initialize(markup)
       lookups = markup.scan(VariableParser)
 
diff --git a/test/unit/migrate_unit_test.rb b/test/unit/migrate_unit_test.rb
new file mode 100644
index 00000000..e9292c02
--- /dev/null
+++ b/test/unit/migrate_unit_test.rb
@@ -0,0 +1,121 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class MigrateUnitTest < Minitest::Test
+  def test_migrate_preserves_valid_markup
+    [
+      "{{a}}",
+      " {{- \ta\n -}} ",
+      "{{a.b['c'].d[5]|default:6,allow_false:true|truncate:7,'..'}}",
+      "{{ a . b [ 'c' ] . d [ 5 ] | default : 6 , allow_false : true | truncate :  4 , '..'  }}",
+      "{%assign x=a.b['c'].d[5]|default:6,allow_false:true|truncate:7,'..'%}",
+      "{% assign x =\na . b [ 'c' ] . d [ 5 ] | default : 6 , allow_false : true | truncate :  4 , '..'  %}",
+      "{% if a and b > c %}A{% elsif d or f contains g %}B{% else %}C{% endif %}",
+      <<~LIQUID,
+        {% liquid
+          if x > 0
+            assign x = x | plus: 1
+
+          endif
+        %}
+      LIQUID
+    ].each do |source|
+      assert_no_migration(source)
+    end
+  end
+
+  def test_migrate_variable
+    with_error_mode(:lax) do
+      assert_migration({
+        %({{ ,|"' }}) => "{{  }}", # no MarkupWithQuotedFragment match, skipping characters
+        %({{ ,|"' 123 }}) => "{{ 123 }}", # MarkupWithQuotedFragment skipped characters
+        "{{  12 34  }}" => "{{  12  }}", # no FilterMarkupRegex match, skipping characters
+        "{{ -12 34 | abs }}" => "{{ -12 | abs }}", # FilterMarkupRegex skipped characters
+        %({{ -12 | '" abs }}) => "{{ -12 |  abs }}", # FilterParser skipped characters
+        "{{ -1 | abs ' plus: 1 }}" => "{{ -1 | abs | plus: 1 }}", # FilterParser unexpected separator
+        "{{ -1 | ! abs }}" => "{{ -1 | abs }}", # ignored non-word characters preceding filter name
+        "{{ 'a' | append WAT: 'b' }}" => "{{ 'a' | append : 'b' }}", # FilterArgsRegex skipped characters
+        "{{ '!' | replace, '!': '?' }}" => "{{ '!' | replace: '!', '?' }}", # FilterArgsRegex unexpected separators
+        "{{!-a-!}}" => "{{ -a- }}", # preserve separators when removing ignored characters
+      })
+    end
+  end
+
+  def test_migrate_expression
+    with_error_mode(:lax) do
+      assert_migration({
+        "{{ (1.9...2.8) }}" => "{{ (1..2) }}", # apply constant range coercion
+        "{{ 1.2.3.4 }}" => "{{ 1.2 }}", # multiple periods allowed by FLOATS_REGEX, truncated by to_f
+        "{{ 1. }}" => "{{ 1.0 }}", # FLOATS_REGEX didn't require digits after the period
+        "{{ .empty }}" => "{{ ['empty'] }}", # skipped character prevents exact literal lookup
+      })
+    end
+  end
+
+  def test_migrate_variable_lookup
+    with_error_mode(:lax) do
+      assert_migration({
+        "{{@-a[b].c-@}}" => "{{ -a[b].c- }}", # VariableParser skipped characters
+        "{{ a!b$c }}" => "{{ a.b.c }}", # VariableParser unexpected separators
+      })
+    end
+  end
+
+  def test_migrate_assign
+    with_error_mode(:lax) do
+      assert_migration({
+        "{% assign!a = b-!%}" => "{% assign a = b- %}", # Syntax skipped characters
+        "{% assign a = @b ! %}" => "{% assign a =  b %}", # Variable skipped characters
+        "{% assign|x=1 %}" => "{% assign x=1 %}", # ensure tag name separated from markup
+      })
+    end
+  end
+
+  def test_lax_migrate_if
+    with_error_mode(:lax) do
+      assert_migration({
+        "{% if@a-@%}Y{% endif %}" => "{% if a- %}Y{% endif %}", # Syntax skipped character
+        "{% if &a contains^b and *c %}A{% elsif %d or$e %}B{% endif %}" =>
+          "{% if  a contains b and  c %}A{% elsif  d or e %}B{% endif %}", # test more expressions
+        "{% if b 1 %}Y{% endif %}" => "{% if b  %}Y{% endif %}", # missing operator with right operand
+        "{% if c == %}Y{% endif %}" => "{% if c == nil %}Y{% endif %}", # operator with missing right operand
+        "{% if!a-!%}T{% endif %}" => "{% if a- %}T{% endif %}", # VariableParser skipped characters
+        "{% if!%}T{% endif %}" => "{% if nil %}T{% endif %}", # VariableParser skipping all characters
+      })
+    end
+  end
+
+  def test_migrate_liquid_tag
+    with_error_mode(:lax) do
+      source = <<~LIQUID
+        {% liquid
+          assign ! a = 1
+          assign a = @b !
+        %}
+      LIQUID
+      expect = <<~LIQUID
+        {% liquid
+          assign   a = 1
+          assign a =  b
+        %}
+      LIQUID
+      assert_migration({ source => expect })
+    end
+  end
+
+  private
+
+  def assert_no_migration(source)
+    assert_equal(source, Liquid::Template.migrate(source))
+  end
+
+  def assert_migration(source_to_expected_output_hash)
+    source_to_expected_output_hash.each do |source, expect|
+      message = "source: #{source.inspect}"
+      assert_equal(expect, Liquid::Template.migrate(source), message)
+      assert_no_migration(expect)
+      assert_equal(Liquid::Template.parse(expect).render!, Liquid::Template.parse(source).render!, message)
+    end
+  end
+end