templa.tcl

# From: https://wiki.tcl-lang.org/page/TemplaTcl%3A+a+Tcl+template+engine                                                                                                                  
source tt.tcl

set template {
    <element><%= $myvar %></element>
}

# Create template engine                                                                                                                                                                   
TemplaTcl::create tt

# Load template from string; alternative is parseFile for file                                                                                                                             
tt parse $template

tt setVar myvar "Hello world"

puts [tt render]