my ($mtab, $mounted);
$mounted = 0;
if($^O eq 'linux') {
  $mtab = '/etc/mnttab';
} else {
  $mtab = '/etc/mtab';
}
open my $mounts, "<$mtab" or die($!);
while(<$mounts>) {
  if($_ =~ /\S+ (\S+) .*/) {
    $mounted = 1 if($1 eq '/opt/mymountpoint');
  }
}