my $hashref = \$devstats->{$nic};
$hashref = \$$hashref->{$_} for @data[5..$#data];
$$hashref = $value;
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should be

my $scalarref = \$devstats->{$nic};
$scalarref = \$$scalarref->{$_} for @data[5..$#data];
$$scalarref = $value;
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This can be simplified to

my $scalarref = \$devstats;
$scalarref = \$$scalarref->{$_} for $nic, @data[5..$#data];
$$scalarref = $value;
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or

my $scalarref = \$devstats;
$scalarref = \$$scalarref->{$_} for @data[4..$#data];
$$scalarref = $value;
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This can be replaced with

sub dive_val :lvalue { my $p = \shift; $p = \$$p->{$_} for @_; $p }

dive_val($devstats, @data[4..$#data]) = $value;
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or

use Data::Diver qw( DiveVal );

DiveVal($devstats //= {}, map \$_, @data[4..$#data]) = $value;
[download]

How these work is explained here.