To start you out, here is code to get a smooth distribution (P is short for percentage):

my $pErr = 5; # for plus/minus 5.
sub MakeP { my $p = $_[0]; $p -= $pErr; $p += int(rand() * 2 * ($pErr 
++ 0.5)); return $p / 100 }

#Test
my @foo;
push @foo, MakeP( 50 ) for 0 .. 20000;
@foo = sort @foo;
while ( @foo )
{
    my $next = shift @foo;
    my $count = 1;
    while ( @foo and $foo[0] == $next ) {
        ++$count; shift @foo }
    printf "%f\t%6d\n", $next, $count;
}
[download]

Note that the distribution is reasonably smooth... but I want it to clump to the middle in either a bell curve or triangular fashion.

Update

I suppose I could randomly choose the width of the distribution, that clumps things... it is less than elegant though.

sub MakeP { 
   my $p = $_[0];
   my $e = 1 + int( rand() * $pErr ); 
   $p -= $e; 
   $p += int( rand() * 2 * ( $e + 0.5 ) ); 
   return $p / 100
}
[download]