Slight obscura; please no mock my style! ;-)

use List::Util qw( reduce pairs );

# Firm talk so perl know I mean it.
    reduce ## abuce
    {      $$a       {
           $$b[0]
    }  +=  $$b[1],$a } \

# It simple now.
my %result => pairs %h1, %h2, %h3, %h4;
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