easily solved with @ref{CfgExec, exec} handles.
@verbatim
-exec:
+exec: {
warcer: ["/bin/sh", "/path/to/warcer.sh"]
wgeter: ["/bin/sh", "/path/to/wgeter.sh"]
aria2c: [
"--on-download-complete", "aria2-downloaded.sh",
"--on-bt-download-complete", "aria2-downloaded.sh"
]
+}
@end verbatim
@file{warcer.sh} contents: