Entering

foo=bar,baz

in the Systremproperties field (in German Systemeigenschaften) of an Ant
build-step of a freestyle project.

Results in the consoleoutput of the build to:
...
BUILD FAILED
Target "baz" does not exist in the project "projectname".
...

The Help text says one can use standardformat of properties files and commas are
allowed there. (Using commas in a properties used by Ant)

A workaround is to use:
foo="bar,baz"