How to break down this obstufication...

First break it up into readable code:

#!/usr/bin/perl
$t=("wrongwaywrongwaywrongwaywrongwaywrongwaywrongwaywrongwaywrongway"
+);
@j=(83,13,11,16,-61,3,60,-4,-63,60,1,-23,25,-43,-23,55,-11,-53,45,-59,
+77,1,10,-5);
my $c=("wrongway yes i said wrongway who else ?");
$m=0;
for ($y=0;$y<$#j+1;$y++){
    $m=$m+$j[$y];
    push(@r,$m);
    print chr ord chr(ord(substr($t,$y+3,1))^ord(chr($r[$y]))^ord chr 
+ord chr ord(chr(ord(substr($c,$y,1)))));
}
print " - ". substr($c,20,8);
sleep $j[5];
[download]

Next we'll cancel out the redundant pairs of chr & ord and remove the (annoying) sleep

#!/usr/bin/perl
$t=("wrongwaywrongwaywrongwaywrongwaywrongwaywrongwaywrongwaywrongway"
+);
@j=(83,13,11,16,-61,3,60,-4,-63,60,1,-23,25,-43,-23,55,-11,-53,45,-59,
+77,1,10,-5);
my $c=("wrongway yes i said wrongway who else ?");
$m=0;
for ($y=0;$y<$#j+1;$y++){
    $m=$m+$j[$y];
    push(@r,$m);
    print chr( ord(substr($t,$y+3,1)) ^ $r[$y] ^ ord(substr($c,$y,1)) 
+);
}
print " - ". substr($c,20,8);
[download]

And now we notice that @r is redundant:

#!/usr/bin/perl
$t=("wrongwaywrongwaywrongwaywrongwaywrongwaywrongwaywrongwaywrongway"
+);
@j=(83,13,11,16,-61,3,60,-4,-63,60,1,-23,25,-43,-23,55,-11,-53,45,-59,
+77,1,10,-5);
my $c=("wrongway yes i said wrongway who else ?");
$m=0;
for ($y=0;$y<$#j+1;$y++){
    $m=$m+$j[$y];
    print chr( ord(substr($t,$y+3,1)) ^ $m ^ ord(substr($c,$y,1)) );
}
print " - ". substr($c,20,8);
[download]

And the code is now pretty obvious. Loop through @j using a for loop on $y. Increment $m by the current value from @j, then XOR a character from $t, one from $c and the current value of $m. Then finally print out a sub string of $c.