Expose javascript regex

app/helpers/ci_variables_helper.rb

@@ -27,4 +27,8 @@ module CiVariablesHelper
       %w(File file)
     ]
   end
+
+  def ci_variable_maskable_regex
+    Maskable::REGEX.inspect.sub('\\A', '^').sub('\\z', '$').sub(/^\//, '').sub(/\/[a-z]*$/, '')
+  end
 end

doc/ci/variables/README.md

@@ -92,10 +92,9 @@ This means that the value of the variable will be hidden in job logs,
 though it must match certain requirements to do so:
 
 - The value must be in a single line.
-- The value must contain only letters, numbers, or underscores.
+- The value must only consist of characters from the Base64 alphabet, defined in [RFC4648](https://tools.ietf.org/html/rfc4648).
 - The value must be at least 8 characters long.
 - The value must not use variables.
-- The value must only consist of characters from the Base64 alphabet, defined in [RFC4648](https://tools.ietf.org/html/rfc4648).
 
 If the value does not meet the requirements above, then the CI variable will fail to save.
 In order to save, either alter the value to meet the masking requirements