=over

=item rand EXPR

=item rand

Returns a random fractional number greater than or equal to C<0> and less
than the value of EXPR.  (EXPR should be positive.)  If EXPR is
omitted, the value C<1> is used.  Automatically calls C<srand()> unless
C<srand()> has already been called.  See also C<srand()>.

(Note: If your rand function consistently returns numbers that are too
large or too small, then your version of Perl was probably compiled
with the wrong number of RANDBITS.)

=back