if ($opt{'c'}) {
    open ( CATLOG, '<', $MAILLOG )
         or die "Can't open $MAILLOG: $!\n";
} else {
    my $ref = tie *CATLOG, "File::Tail",(
        name  => $MAILLOG,
        tail  => -1
    ) or die "Can't tie $MAILLOG: $!\n";
}
while (my $line = <CATLOG>) {
    # ...while loop code here...
}