How to get rid of unwanted characters based on a varying pattern?

[Reginald Thuss]

If I have the following string variable with these entries:

median_age_____
median_age_group1__
median_age_group23___
median_age_group23456
median_age_group234__
...

What is the best way to get the following, given that at the end of each string "_" is not consistent in terms of the number of characters it takes up?

median_age
median_age_group1
median_age_group23
median_age_group23456
median_age_group234
...

[Andrew Musau]

* Example generated by -dataex-. To install: ssc install dataex
clear
input str21 var1
"median_age_____"      
"median_age_group1__"  
"median_age_group23___"
"median_age_group23456"
"median_age_group234__"
end

gen wanted = ustrregexra(var1,"([^[a-zA-Z0-9]]+$)", "")

Res.:

. l

     +-----------------------------------------------+
     |                  var1                  wanted |
     |-----------------------------------------------|
  1. |       median_age_____              median_age |
  2. |   median_age_group1__       median_age_group1 |
  3. | median_age_group23___      median_age_group23 |
  4. | median_age_group23456   median_age_group23456 |
  5. | median_age_group234__     median_age_group234 |
     +-----------------------------------------------+

[Bjarte Aagnes]

gen var2 = ustrregexrf(var1, "_+$", "")