How to correctly compose a regular expression for working with a variable in Asterisk?

Question

Asterisk

The task is to insert into the dialplan a check of the EXTEN value, for the presence and trimming of a space at the end of EXTEN, if any. I understand that you need to use ExecIf, REGEXP, but various handler options are either "crutch" or do not work

Answer 1

Shadowplay ,
ExecIf(${REGEX(" $" ${foo})}?Set(foo=${foo:0:-1})