Ok, this is my first japh. I haven't got it down to four lines, but 5 is almost 4 for really small values of 5.

If you don't want clues, don't look up the ACA. I put it in the title because I wanted it to be more personal than "My first JAPH", but I didn't want to put too much in the title for those who have fun with de-obfuscating.

@ca=(sub{@kp=split(//,shift);$c=shift;$p2{' '}=' ';$C2{' '}=' ';foreac
+h(@kp,
'a'..'z'){if(!exists $p2{$_}){$k=chr(ord('A')+(($a++)+$c)%26);$p2{$_}=
+$k;
$C2{$k}=$_;}}},sub{$t=shift;$h=shift;foreach(split(//,$t)){$r=$r.($$h{
+$_});}
return $r;});$ca[0]->('thequickbrownfoxjumpsoverthelazydogs',10);print
+ 
$ca[1]->('ZOCK FWUKLMT BMTE LFQR',\%C2)."\n";
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