# I assume 'snmpauto' is the name of a file.
use File::Spec;
my $snmp_file = find_snmpauto();

sub find_snmpauto {
    my $filename = 'snmpauto';
    my @paths = qw(c:\\ /root);

    for (@paths) {
        my $name = File::Spec::catfile($_,$filename);
        return $name if -f $name;
    }

    # we hit here only if no file was found.
    die "Can't find a file '$filename' in the search path (path includes:"
       .join(', ',@paths)
       .")\n";
}