#!/usr/bin/perl --
use strict; use warnings;
use LWP;
use Data::Dump();
sub LWP::Protocol::http::SocketMethods::format_request {
    package LWP::Protocol::http::SocketMethods;
    my( $socket, $method, $fullpath, @h ) = @_;
#~     my $req_buf = $socket->Net::HTTP::Methods::format_request($method, $fullpath, @h, 'Keep-Alive',666); ## fail, adds another header
    my $req_buf = $socket->Net::HTTP::Methods::format_request($method, $fullpath, @h );
    $req_buf =~ s{Keep-Alive: 300}{Keep-Alive: 30}g; ## win, removes existing header
    Data::Dump::dd( $req_buf );
    return $req_buf;
}
LWP::UserAgent->new( keep_alive=>1 )->get( q{http://127.0.0.1:80/} )->dump;
__END__
"GET / HTTP/1.1\r\nTE: deflate,gzip;q=0.3\r\nKeep-Alive: 30\r\nConnection: Keep-Alive, TE\r\nHost: 127.0.0.1:80\r\nUser-
Agent: libwww-perl/6.15\r\n\r\n"
HTTP/0.9 200 Assumed OK
Client-Date: Tue, 24 Apr 2018 23:25:20 GMT
Client-Peer: 127.0.0.1:80
Client-Response-Num: 1

Echo: GET / HTTP/1.1\r
Echo: TE: deflate,gzip;q=0.3\r
Echo: Keep-Alive: 30\r
Echo: Connection: Keep-Alive, TE\r
Echo: Host: 127.0.0.1:80\r
Echo: User-Agent: libwww-perl/6.15\r
Echo: \r\n