Nautilus script to perform one operation on multiple selected files?

I have a Nautilus script that I would like to modify so it performs a single operation using multiple selected files as input. Can someone please explain how to achieve this? I tried command $NAUTILUS_SCRIPT_SELECTED_FILE_PATHS and what the script does is execute command file1, then command file2 as two discrete operations. That doesn't work for my use case, instead I need the script to execute command file1 file2. If it matters, I am using it with the command align_image_stack which needs 2 or more image files as input. I started Nautilus from a terminal to see error messages and I get *"align_image_stack: At least two files need to be specified"*. I've tested a few commands shown below, but all produce the same error message. I think the problem is the variable $NAUTILUS_SCRIPT_SELECTED_FILE_PATHS produces newlines, but I don't know how else to capture selected file paths. align_image_stack "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" align_image_stack $(echo "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS") align_image_stack printf("$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS") echo -n "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" | xargs -I align_image_stack "{}"