despite what it says there in the help file:
alias testin {
var %input = $input(this is a $ctrl Test,nv)
if (%input == $yes) { echo -s $+($,input) returned %input }
if (%input == $no) { echo -s $+($,input) returned %input }
if (%input == $cancel) { echo -s $+($,input) returned %input }
}
or
alias testin {
var %input = $input(this is a $ctrl Test,eo)
if (%input) { echo -s $+($,input) returned %input }
}
both work, so I think that the identifier has changed, I know in older versions, numbers, not letters, were used for the button options.
Maybe the behaviour has changed but the comment remains.