Matches Function issue:Fetch record task,unable use Matches in criteria

Matches Function issue:Fetch record task,unable use Matches in criteria



Using Matches  function for a crateria to   Fetch record   do has  a bug or not supported 

f or example
  1. matchedRecords  =  formName  [Single_Line.matches("abc.{4}d")];
     abc. {4}d    is  regular expression    
     return   variable  matchedRecords     contains all record from in  formName. 
     it  means regular expresstion  do not work。
   
   how let regular expression do work in matches function at fetch record task?