Construct the hash with the static values first, then add the dynamic ones, then call the sub.

use strict;
use warnings;

my $added = [
    {   link => "/var/www/docs",
        name => "mydocs",
    },
    {   link => "/var/www/read",
        name => "letters",
    }
];

my @keys = qw( link  name );

my $success;

foreach my $send_to (@send) {

    my %send_vals = (
        to      => 'send_to',
        account => 'to_account',
        name    => 'name',
        subject => 'subject',
        title   => 'title',
        type    => 'docs',
    );
    for my $hash (@$added) {
        for my $key (@keys) {
            $send_vals{$key} = $hash->{$key};
        }
    }
    $success = sent (\%send_vals);
}
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Untested because you haven't defined @send or sent() anywhere.