References are good. Here's a working version - you should be able to figure it out from this:

#!/usr/bin/perl

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

sendmail(\{to=>'koszta@seznam.cz', from=>'admin@server.com', data=>'hi
+ from server', subject=>'msg body'});

sub sendmail {
        my $param = shift;
        my $email= MIME::Lite->new(
            From=>"$$param->{'from'}",
            To=>"$$param->{'to'}",
            Subject=>"$$param->{'subject'}",
            Data=>"$$param->{'data'}"
        );
        # debug output
        print "I would now send from $$param->{'from'} to $$param->{'t
+o'}:\n";
        print "Subject: $$param->{'subject'}\n\n";
        print "$$param->{'data'}\n";
        # disable sending as I'm only testing :-)
        # $email->send;
}
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