p4raw-id: //depot/perl@21435
The number 0, the strings C<'0'> and C<''>, the empty list C<()>, and
C<undef> are all false in a boolean context. All other values are true.
-Note that while 0, 0.0 and C<'0'> are false, C<'0.0'> and C<'0e0'> are
-true, but evaluate to 0 in a numeric context.
-
=head2 Statement Modifiers
Any simple statement may optionally be followed by a I<SINGLE> modifier,