=over

=item rand EXPR
X<rand> X<random>

=item rand

Returns a random fractional number greater than or equal to C<0> and B<less>
than the value of EXPR.  (EXPR should be positive.)  If EXPR is
omitted, the value C<1> is used.

    my $num1 = rand();        # Random float at least 0 and below 1
    my $num2 = rand(7);       # Random float at least 0 and below 7
    my $num3 = int(rand(10)); # Random integer at least 0 and below 10

B<Notes:>

=over

=item *

Calling C<rand> automatically calls L<C<srand>|/srand EXPR> unless
srand has already been called.

=item *

Currently EXPR with the value C<0> is special-cased as C<1>. This was
undocumented before Perl 5.8.0 and is subject to change in future versions of
Perl.

=item *

As of Perl v5.20.0 C<rand()> uses the C<drand48> pseudorandom number generator
(PRNG) to generate numbers that appear random but are deterministic.
It is sufficient for games, generating test data or cases where repeatability is needed.

=back

=over

=item B<Security:>

B<C<rand> is not suitable for anything related to security, authentication or encryption.>
Do not use it for generating passwords, session ids, authentication tokens, salts, or encryption keys.
The return values are predictable, and systems that rely on C<rand> are easily broken.

A number of third-party CPAN modules offer access to system sources of randomness,
or random number generators that are suitable for security purposes, including:

=back

=over

=item * L<Crypt::SysRandom>

=item * L<Crypt::URandom>

=item * L<Crypt::PRNG>

=back

=back