A hash is initialised with a list of key-values pairs, so there must be an even number of items in the list. This error means you're trying to initialise a hash with a list that has an odd number of elements (and doesn't come from the snippet of code you posted).

my %h1 = ( 1, 2 ); # OK - same as ( 1 => 2)
my %h2 = ( 1    ); # Not OK - make no sense
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Is it important? I'd say it probably is. Something is happening in your data that you haven't anticipated. Go back to your data and find out what's causing the error.