1 files changed, 20 insertions, 5 deletions
diff --git a/lib/gitlab/ci/pipeline/expression/lexeme/matches.rb b/lib/gitlab/ci/pipeline/expression/lexeme/matches.rb
index cd17bc4d78b..ecfab627226 100644
--- a/lib/gitlab/ci/pipeline/expression/lexeme/matches.rb
+++ b/lib/gitlab/ci/pipeline/expression/lexeme/matches.rb
@@ -8,21 +8,36 @@ module Gitlab
           class Matches < Lexeme::Operator
             PATTERN = /=~/.freeze
 
-            def initialize(left, right)
-              @left = left
-              @right = right
-            end
-
             def evaluate(variables = {})
               text = @left.evaluate(variables)
               regexp = @right.evaluate(variables)
 
               regexp.scan(text.to_s).any?
+
+              if ci_variables_complex_expressions?
+                # return offset of first match, or nil if no matches
+                if match = regexp.scan(text.to_s).first
+                  text.to_s.index(match)
+                end
+              else
+                # return true or false
+                regexp.scan(text.to_s).any?
+              end
             end
 
             def self.build(_value, behind, ahead)
               new(behind, ahead)
             end
+
+            def self.precedence
+              10 # See: https://ruby-doc.org/core-2.5.0/doc/syntax/precedence_rdoc.html
+            end
+
+            private
+
+            def ci_variables_complex_expressions?
+              Feature.enabled?(:ci_variables_complex_expressions, default_enabled: true)
+            end
           end
         end
       end