subfile('iocommon');

sub subfile {
    my($f)=@_;
    my($w);
    # %GOT_HA seems to be a variable emulating %INC maybe?
    if(!$GOT_HA{$f}){
        # where do $my_base_loc, $subslocation and $ds come from?
        # is that a case for using File::Spec instead?
        $f=("$my_base_loc$subslocation$ds$f.sub");

        # you need error handling here in case the file is not found:
        # Are $t and $rep global variables? What are they used for?
        $t=open (IE,"$f") or die "Couldn't open '$f': $!";
        $rep=($t)?'OK':$!;

        # What does that do? Maybe you want to look in that log for the error report?
        db("subfile $f",$rep);

        # Are you using strict; at all? You really should!
        # This whole section is likely better written as
        # my $w = do { local $/; <IE> };
        @tt=<IE>;
        close(IE);
        while(@tt){
            $l=trim(shift @tt);
            $w.=$l."\n";
        }
        eval($w);
        if (my $err = $@) {
            die "Error in evaluating '$f': $!";
        };
        $GOT_HA{$f}=1;
    }
}