IIRC solaris uses /etc/mnttab, so you could do something like this:

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');
  }
}
[download]

Sorry, I messed up with the file names. Obviously it needs to be the other way around ;)

if($^O eq 'linux') {
  $mtab = '/etc/mtab';
} else {
  $mtab = '/etc/mnttab';
}
[download]

You could (and probably should) specify solaris for the else-clause, but I'm not sure what $^O yields on Solaris.. Probably just 'solaris'.

Also don't forget to close the file after all that:

close $mounts;

you could (and probably should) specify solaris for the else-clause, but I'm not sure what $^O yields on Solaris.. Probably just 'solaris'.

This is somewhat off topic... it all depends on what you are trying to do but note there is a difference in output between $^0, uname, and $Config{archname}. Below is some output from different OSes for comparison. The following code was used:

#!/usr/bin/perl

use strict;
use Config;

my $os_OS = $^O;
my $config = $Config{'archname'};

my @uname = `uname -a`;
chomp( my $os = shift @uname );
$os =~ s/^(\w+)\s.*/$1/;

print "Uname -> $os\n";
print "\$^O -> $os_OS\n";
print "Config -> $config\n";
[download]

Linux
Uname -> Linux
$^O -> linux
Config -> x86_64-linux-gnu-thread-multi

Solaris 5.9 and 5.10
Uname -> SunOS
$^O -> solaris
Config -> sun4-solaris-64int

AIX 6.1
Uname -> AIX
$^O -> aix
Config -> aix-thread-multi

Also be aware that $^O returns the architecture the perl binary was built on not the OS you are running on. That can be misleading, for example:

OS400 PASE
Uname -> OS400
$^O -> aix
Config -> aix

See the discussion OS400 PASE - architecture? for details.

regexes