Good point.

A simple way to see if your script finished running is to add a few more print statements before your closing html tags, like so:

 
print MYOUTFILE "Testing 1 2 3"; #write text, no newline

print MYOUTFILE "\n"; #write newline

print "Wrote to file \n"; #if this doesn't show in the browser, 
                          #the script didn't write to the file

close(MYOUTFILE);

print "Closed MYFILE \n"; #if this doesn't show in the browser, 
                          #the script didn't close the file

print "</body> </html>\n";
[download]

In general, tachyon's CGI Help Guide has been invaluable when I was figuring out CGI.

Update: Forgot to do ID tags.