The function returns a hash. What you do with that hash is up to you. You haven't shown your program, so I can only give you general advice.

One approach would be to set up %ENV with the newly found values. Another one would be to merge %ENV with the newly found values, as you (and the example) show. A third approach would be to keep the two sets of values separate.

To simulate running under the login environment as closely as possible, %ENV = get_login_env() will certainly do that, but in the process, you lose any indication that your program is running as cron job. In general, I think the approach of merging %ENV and the values from the login environment, with the values from the login environment taking precedence is a good one.

Well, it works from the prompt but not via cron.

use strict;
use warnings;
use MIME::Lite;

# from the link you gave
sub get_login_env {
  local %ENV;
  my $shell = shift || (getpwuid($<))[8];
  my $env = `echo env | perl -e 'exec {"$shell"} -sh'`;
  if (wantarray) {
    my @pieces = ( $env =~ m/^(.*?)=((?:[^\n\\]|\\.|\\\n)*)/gm );
    s/\\(.)/$1/g foreach @pieces;
    return @pieces;
  }
  else {
    return $env;
  }
}

%ENV = (%ENV, get_login_env());
my $mailvar = $ENV{'TESTMAILUSRS'}; 
my @mailUsers;
my $msg = new MIME::Lite();
$msg->build(
  From            =>    'us@here.com',
  Subject        =>    'Email from perl via cron',
  Type            =>    'text/html',
  Data            =>    'testing',
    Debug            => 1

);

for (split /[\s\n]/, $mailvar){
    if($_){
        $msg->add(To    =>    $_);
    }
}

eval { $msg->send };
die "MIME::Lite->send failed: $@\n" if $@;
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