Is a global property returning the last value returned by return from a handler, from an engine function, or from an engine command which sets the result.
if the result is not empty then exit mouseUp
Many commands (such as go and find) set the value of the result function when they finish. In most cases, if the result is empty, the command was successful; if the result is not empty, the command failed and the result contains an error message. See the specific command for information about whether it sets the result function.
If a command fails because of an operating-system error (such as a file not being available), the sysError function returns the error message that the operating system reported to LiveCode. In this case, you can use the sysError function to get additional information about the error if the result is not empty.
myMessage put the result
and the "myMessage" handler contains the line
return "some value"
the text "some value" appears in the message box when the handler runs. You can use this capability to return an error message if a custom message handler fails.
If you need to check the result, do so immediately after the statement whose result you want to check (or save the value of the result in a variable for later checking). This ensures that the result you are checking is the correct one, not a value set by a later statement.