Template substitution in Emacs?

[Marcin Borkowski <mbork@wmi.amu.edu.pl>]

Hi there,

assume that I want to insert an (almost) constant string in Emacs
buffer.  For instance, it may be a string of the form

"I am a {my-variable}."

However, I want the "{my-variable}" part to be, well, variable: I want
to substitute the current value of `my-variable' for this.  So that

(setq my-variable "sentence")
(insert (template-substitute "I am a {my-variable}."))

would insert "I am a sentence." at point.

Of course, I could just use (format "I am a %s." my-variable), or even
define a function to do this.  The drawback would be that if the
"template" is a user-customizable thing, then the user would have to
supply %s's and not meaningful names.  What's more, the /order/ of the
substituted strings would be hardcoded in the "template".

Obviously, I could come up with such a function within 10-15 minutes or
so.  But why reinvent the wheel?  Is there anything like this in Emacs?

TIA,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Adam Mickiewicz University