It seems that accessing parameters with build command 'Execute shell' has strange syntax when building with URL request and multiple parameters.

For example, when I trigger my build with URL:
http://server/job/myjob/buildWithParameters?token=TOKEN&PARA1=Value1&PARA2=Value2

and try to echo those string parameters, I need to use the following syntax:
echo $PARA1
echo ${para2}

For example this alternative doesn't work. It is echoing only blank values:
echo ${para1}
echo $PARA2

This seems to be somewhat similar to this:
https://issues.jenkins-ci.org/browse/JENKINS-16639