Its what you would expect when hash element assignment is done more than once. After expansion, args are processed left to right. The last one "wins".

#!/usr/bin/perl -w
use strict;
use Data::Dump qw(pp);

my $subargs = {a=>1, b=>2, subkey1 => 3};
my $r = { %$subargs, subkey1 => 'subval1', subkey2 => 'subval2'};

pp $r;
#prints:
#{ a => 1, b => 2, subkey1 => "subval1", subkey2 => "subval2" }
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