This is helping to narrow down the problem. I made two small changes to your code and now I can replicate the problem.

#!/usr/bin/perl -d

use LWP;
use strict;
use warnings;

my $ua = new LWP::UserAgent;

my $r = $ua->get("http://groups.yahoo.com");

if ($r->is_success)
{
    if ($r->content =~ m/^\s+\S$/m)
    {
    print "I saw some trailing spaces...\n";
    }
    else
    {
    print "Oppsie! I did not see any trailing spaces...\n";
    }
}
else
{
    die "Failed miserably\n";
}
[download]

I updated the regex to (I believe) properly look for individual lines with leading spaces and some text. Then I tried a different web page. The problem now appears.

If you actually print out the content $ua->content, you'll see that LWP doesn't print any of the leading spaces that Mozilla View Source does show!

I'd really like to understand what's happening here!

Andy

@_="the journeyman larry disciple keeps learning\n"=~/(.)/gs,
print(map$_[$_-77],unpack(q=c*=,q@QSdM[]uRMNV^[ni_\[N]eki^y@))
[download]