Start by breaking it down. Remember that y/// is the same as tr///.

Looking at perlvar we see that $; is $SUBSCRIPT_SEPARATOR, $^ is $FORMAT_TOP_NAME, $" is $LIST_SEPARATOR, $& is $MATCH and $/ is $INPUT_RECORD_SEPARATOR.

So what do we have now?

use English;
die $SUBSCRIPT_SEPARATOR!~tr//.-~/c.$SUBSCRIPT_SEPARATOR.
([$FORMAT_TOP_NAME=~/./g]&~$LIST_SEPARATOR).
$MATCH.($SUBSCRIPT_SEPARATOR&{}).$INPUT_RECORD_SEPARATOR
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That should as clear as mud :)