$x = join'', shuffle map{ ($_)x10 } 'a'..'j'; 
print $x;;
ahgbjgbcjjgbbfdiadeehgdhcijjebaaegehccdfdbejcgdhehcbehdgcihiffgefjijabfbjadfaaiiiahfegihdgdaccicffjb

$y = $x; 
$y =~ tr[abcdefgh][12341234]; 
print $y;;
1432j323jj32224i141143443ijj121113143342421j3344143214433i4i22312jij1222j14211iii14213i4434133i322j2

$i=0; $j=0; 
$y =~ s[([ij])]{ $1 eq 'i' ? ( ($i^=1) ? '1' : '2' ) : ( ($j^=1) ? '3' : '4') }ge; 
print $y;;
1432332343322241141143443243121113143342421433441432144331422231231412223142112121421314434133232242