Page variables, set from a URL parameter

It would be useful in some situations to have a Confluence page where parts of content could be set from the URL.

For instance, we have a page telling users how to set Java properties from the command-line (-Dxx=yy):

http://confluence.atlassian.com/display/JIRA/Setting+properties+and+options+on+startup

This page has an example property, -Dfile.encoding, hardcoded. It would be cool if one specify a different property from the URL, and send this to customers:

http://confluence.atlassian.com/display/JIRA/Setting+properties+and+options+on+startup?prop=-Djira.jelly.on%3dtrue

Similarly, when applying 'patch' jars, the procedure is always the same, but the name of the .jar file differs.