Hi,
Well this is my first JAPH. Its not that tricky but I'm new to this :P.

undef $i; 
print grep(s*^([a-z]{$i,})+$*$1*,@{[pack('aaaa',map{ lc chr } map{++$i
+==1?$_+9:$i==2?$=+5:$i==3?$_+13:$i==4?$_+$i:--$i;}(65..80))]});
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