There's no reason for that warning. You need to double check the code you're copying:

$ perl -Mstrict -we 'my @a = qw(a b c d);  my %h = map { $_++ } @a'
$ perl -Mstrict -we 'my @a = qw(a b c d e);my %h = map { $_++ } @a'
Odd number of elements in hash assignment at -e line 1.
$
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s**lil*;  $*=join'',sort split q**;  s;.*;grr; &&s+(.(.)).+$2$1+; $; =
qq-$_-;s,.*,ahc,;$,.=chop for split q,,,reverse;print for($,,$;,$*,$/)
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