Update: this behaviour is now enabled in Twine 1.4, so this script code is no longer necessary.

The following code, when placed in a script passage, changes <<display>> so that you can use variables and operators in it, such as <<display $passage>>.

version.extensions.displayMacro={major:2,minor:0,revision:0};macros.display={handler:function(place,macroName,params,parser){
try{var output=eval(parser.fullArgs()); new Wikifier(place,tale.get(output.toString()).text);}
catch(e){throwError(place,"bad expression: "+e.message);}}};

A quick and untidy alternative to using this code is to just use <<print tale.get($passage).text>> in place of <<display $passage>>
_{Feel free to report any bugs to @webbedspace.}