$SYS_TYPE=1;
...
if ($SYS_TYPE == 1) {

##</code><code>##

$sys_type = "AIX";
...
if ($sys_type eq "AIX") {

##</code><code>##

open (DF, $FILE) || die "Can't Open File: $FILE\n";

##</code><code>##

open my $df, "<", $file or die "Can't Open File: $file: $!\n