Fix spelling in perlopentut

Author: pjcj

pod/perlopentut.pod

@@ -364,7 +364,7 @@ the first example like this:
 When you call C<open> this way, Perl invokes the given command directly,
 bypassing the shell. As such, the shell won't try to interpret any
 special characters within the command's argument list, which might
-overwise have unwanted effects. This can make for safer, less
+otherwise have unwanted effects. This can make for safer, less
 error-prone C<open> calls, useful in cases such as passing in variables
 as arguments, or even just referring to filenames with spaces in them.