This function places an advisory lock on a variable, subroutine,
or referenced object contained in I<THING> until the lock goes out
-of scope. This is a built-in function only if your version of Perl
-was built with threading enabled, and if you've said C<use Thread>.
-Otherwise a user-defined function by this name will be called.
+of scope.
+
+lock() is a "weak keyword" : that means that if you've defined a
+function by this name, this function will be called instead.
+(However, if you've said C<use Thread>, lock() is always a keyword.)
See L<Thread>.
=item log EXPR