As Walter says, your example script will never execute because of the syntax error so try catch inside the file is no good.
However, a try... catch statement in the caller of the file would trap the error. So:
try
nameoflongscript %invoke long script
catch ME
disp(ME)
end
would work.
Alternatively, to detect such parse errors before actually running the script, you could use mlint to analyse the file, or the undocumented mtree to get the parse tree of the file. Either of these will tell you if there are any parse error.
