=over =item lock THING X<lock> This function places an advisory lock on a shared variable or referenced object contained in I<THING> until the lock goes out of scope. The value returned is the scalar itself, if the argument is a scalar, or a reference, if the argument is a hash, array or subroutine. L<C<lock>|/lock THING> is a "weak keyword"; this means that if you've defined a function by this name (before any calls to it), that function will be called instead. If you are not under C<use threads::shared> this does nothing. See L<threads::shared>. =back