my $last = '';
while (my $line = <$fh>) {
    if (    $last =~ m/USB\d*::0x[0-9a-fA-F::]+0x[0-9a-fA-F]+::[0-9a-fA-F]+INSTR$/ 
        and $line =~ m/USB\d*::0x[0-9a-fA-F::]+0x[0-9a-fA-F]+::[0-9a-fA-F]+INSTR$/) 
    {
        print "$last$line";
    }
    $last = $line;
}

##</code><code>##

my $content = do{local $/;<$fh>};
while ($content =~ /((?:USB\d*::0x[0-9a-fA-F::]+0x[0-9a-fA-F]+::[0-9a-fA-F]+INSTR\n){2})/g) {
    print $1;
}