Would something like this work?

#! perl -slw
use strict;
use List::Util qw[ shuffle ];

our $N ||= 10;
our $E ||=  5;

my @a = (shuffle 1 .. $N)[ 0 .. $E ];
my @b = (shuffle 1 .. $N)[ 0 .. $E ];
my @c = (shuffle 1 .. $N)[ 0 .. $E ];
my @d = (shuffle 1 .. $N)[ 0 .. $E ];

my %comp;
$comp{ $_ }{a} = 'a' for @a;
$comp{ $_ }{b} = 'b' for @b;
$comp{ $_ }{c} = 'c' for @c;
$comp{ $_ }{d} = 'd' for @d;

print "     : a b c d\n--------------";
printf "%4s : %s\n", $_, 
    join ' ', map{ $_||'-' } @{ $comp{ $_ } }{ 'a'..'d' }
    for sort{$a<=>$b} keys %comp;

__END__
c:\test>528473
     : a b c d
--------------
   1 : - - c -
   2 : a - c d
   3 : a b - -
   4 : a b c -
   5 : a b c d
   6 : a b - d
   7 : - b - d
   8 : - - c d
   9 : - - c -
  10 : a b - d

c:\test>528473 -N=10 -E=8
     : a b c d
--------------
   1 : a - c d
   2 : a b c d
   3 : a b c d
   4 : a b - d
   5 : a b c d
   6 : a b c d
   7 : a b c d
   8 : - b c -
   9 : a b c d
  10 : a b c d
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