use strict;
use File::Spec::Functions;

my %root = (
  MSWin32 => "C:\\Data",
  solaris => "/var/data",
);

my $ROOTDIR = $root{$^O} or die "Unknown platform";

my $file1 = canonpath("$ROOTDIR/data.txt");
print "$file1\n";
my $file2 = canonpath("$ROOTDIR/../input/data2.txt");
print "$file2\n";