Set a custom HTTP User-Agent in Perl with WWW::Mechanize

mechanize-user-agent.pl

use WWW::Mechanize;

my $initial_user_agent = 'Mozilla/5.0 (Linux; U; Android 2.2; de-de; HTC Desire HD 1.18.161.2 Build/FRF91) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1';
my @user_agents = (
    'Mozilla/5.0 (Windows; U; Windows NT 6.1; nl; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13',
    'Mozilla/5.0 (iPad; U; CPU iPhone OS 3_2 like Mac OS X; en-us) AppleWebKit/531.21.10 (KHTML, like Gecko) Mobile/7D11',
    'Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_3 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8J2 Safari/6533.18.5',
);

# Set an initial custom header with the contructor
my $mech = WWW::Mechanize->new( agent => $initial_user_agent );

# get a page and print current URI (WWW::Mechanize follows redirections)
$mech->get( 'http://www.facebook.com' );
print sprintf( "User-Agent %s\n  redirects to: %s\n\n", $initial_user_agent, $mech->uri() );

foreach my $http_user_agent (@user_agents) {
    # dynamically set custom HTTP User-agents
    $mech->add_header( 'User-agent' => $http_user_agent);

    $mech->get( 'http://www.facebook.com' );
    print sprintf( "User-Agent %s\n  redirects to: %s\n\n", $http_user_agent, $mech->uri() );
}

# $ perl ./mechanize-user-agent.pl
# User-Agent Mozilla/5.0 (Linux; U; Android 2.2; de-de; HTC Desire HD 1.18.161.2 Build/FRF91) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1
#   redirects to: http://m.facebook.com/?w2m&refsrc=http%3A%2F%2Fwww.facebook.com%2F&_rdr
# 
# User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; nl; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13
#   redirects to: http://www.facebook.com
# 
# User-Agent Mozilla/5.0 (iPad; U; CPU iPhone OS 3_2 like Mac OS X; en-us) AppleWebKit/531.21.10 (KHTML, like Gecko) Mobile/7D11
#   redirects to: http://m.facebook.com/?w2m&refsrc=http%3A%2F%2Fwww.facebook.com%2F&_rdr
# 
# User-Agent Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_3 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8J2 Safari/6533.18.5
#   redirects to: http://m.facebook.com/?w2m&refsrc=http%3A%2F%2Fwww.facebook.com%2F&_rdr