I don't know where you got PERL_LWP_USE_HTTP_1.0, but when I look for anything like that, this is what I get: 

ceidem@eidem ~$ cd /usr/lib/perl5/site_perl/5.8/
ceidem@eidem /usr/lib/perl5/site_perl/5.8$ grep -r PERL_LWP_USE_HTTP L
+WP 
LWP/UserAgent.pm:if ($ENV{PERL_LWP_USE_HTTP_10}) {

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In reply to Re^2: Forcing HTTP/1.0 and mangling headers by yam
in thread Forcing HTTP/1.0 and mangling headers by yam

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