The trick to LWP authentication is subclassing LWP::UserAgent.

package MyAgent;

use base 'LWP::UserAgent';

sub get_basic_credentials {
    return 'admin', 'password';
}

package main;

my $agent    = MyAgent->new;
my $response = $agent->get( 'http://192.168.0.1/st_devic.html' );

print $response->code;
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WFM