regexp to capture only certain length of characters

Hi, I'm trying to capture words with 4 characters only. A word consists or alphanumeric characters.(no symbols of white space)

str4='4-44g 4541 75872 a4cd stuvw';
 patt4='(\w{4,4})';
 regexp(str4,patt4,'match')

I'm expecting 4541 a4cd as the correct answer. However my code outputs stuv & 7587 in addition. How can I correct this

Answer 1

[Rashmil Dahanayake]

 This could be the solution

 str4='4-44g 4541 75872 abcd stuvw';
  patt4='\<\w{4}\>';
  regexp(str4,patt4,'match')

[Azzi Abdelmalek]

This doesn't work for underscore. For example

str4='4-44g 454_ 75872 abcd stuvw'

Answer 2

[Azzi Abdelmalek]

str4='4-44g 4541 75872 a4cd stuvw';
regexpi([' ' str4 ' '],'(?<=[^0-9,a-z])[0-9,a-z]{4}(?=[^0-9,a-z])','match')