while(my $line=<$FH[$i]>){

<$FH[$i]> doesn't work for syntactic reasons, i.e. special parsing rules apply for <...>, and only simple expressions like <$fh> can be handled.

Use readline $FH[$i] instead, if you don't want to use an intermediate variable.

Update: also note that whitespace isn't allowed either, i.e. < $fh > and <$ fh> won't work... it has to be exactly <$fh>.