Global variable "not defined" - applescript

Question

My AppleScript examines an image file and outputs some of that information. I need this information as normal output (stdout) of the script for further processing (in an InDesign script). But as soon as I open an image file in my AppleScript, the global variable which is meant to hold the result, gets lost.
This is fine (but useless):
global result
set result to "initialised"
set imgfile to POSIX file "/Users/hell/Pictures/interesting_stuff.jpg" as alias
tell application "Image Events"
-- start the Image Events application
launch
set result to "new text"
end tell
return quoted form of result
The following script is what I want, but throws the error "The variable 'result' is not defined (-2753)"
global result
set result to "initialised"
set imgfile to POSIX file "/Users/me/Pictures/interesting_stuff.jpg" as alias
tell application "Image Events"
-- start the Image Events application
launch
-- open image file
set img to open imgfile
-- here would go some commands about img instead of "new text"
set result to "new text"
-- close image file
close img
end tell
return quoted form of result
What is the problem here and how can I get the result out of my script?

Answer 1

result is a special identifier in AppleScript, which you may notice in Script Editor is printed in a different colour/font/style to other variable names you use. It's an AppleScript property that always contains the value returned by the command that is executed immediately before it.
The solution is most likely to choose a different word other than result for your identifier.
As your script stands, you also don't need to declare the variable as a global, since there are no scoping issues in your script that require access to variables outside of its block, which becomes a consideration when creating handlers or script objects.