if object_id('dbo.GetCurrentOrDefault') is not null drop function GetCurrentOrDefault

go

create function GetCurrentOrDefault(@valueOrDefault nvarchar(17)) returns nvarchar(17)
begin
    declare @current_value as nvarchar(17);
    declare @default_value as nvarchar(17);
    declare @value_separator_index as int

    select @value_separator_index = charindex('|', @valueOrDefault)

    if @value_separator_index = 0 return null

    select @current_value = substring(@valueOrDefault, 0, @value_separator_index)
    select @default_value = substring(@valueOrDefault, @value_separator_index + 1, len(@valueOrDefault) - @value_separator_index + 1)
    return iif(@valueOrDefault like '{%}|%', @default_value, @current_value)
end

go

declare @env as nvarchar(51) = N'{Environment}|production'
declare @ver as nvarchar(59) = N'{Version}|3.9.0'

select @env = dbo.GetCurrentOrDefault(@env)
select @ver = dbo.GetCurrentOrDefault(@ver)

if @env is null raiserror ('Invalid environment: ' + @env, 16, 1)
if @ver is null raiserror ('Invalid version: ' + @ver, 16, 1)

.GetSql().Format(new { Environment = "test", Version = "4.0.0" })