Regex: Match upto at the end of a string only one optional word character if found : I want to match an optional "s" if present at the end of the string. Other than "s", it cannot have any "word" character. Digits, Symbols are fine. 

**Note:** It could be a two or three word search as well, for example "he_mans" or "he mans" while "he manity" or "he manned" etc are wrong. What I care about is how it **ends** 

**True examples**

     // This two examples below must return true
     "fsl_mdl" matches ".*" + "mdl" + "[^a-rt-z][s]?.*" // returns false
     "eco_mdl_pipe" matches ".*" + "mdl" + "[^a-rt-z][s]?.*" // returns false"
     

**False examples**

    // The example must return false
    "fonneded" matches ".*" + "fonned" + "[^a-rt-z][s]?.*" 



     
