# ... prompt and read user input ... then:

chomp $l, $t, $w;


##</code><code>##

my $Usage = "Usage: $0 LOT# W# tester#\n";

die $Usage unless ( @ARGV==3 and join(" ",@ARGV) =~ /LOT\d+ W\d+ tester\d+/ );

my ( $l, $w, $t ) = @ARGV;

print "Command line args were:\n $l\n $w\n $t\n";

my $sdtfile = "C:\\bzip\\sdt.log";
if (open (MAPFILE, "< $sdtfile")) {
    my @lines = <MAPFILE>;
    chomp @lines;

    my @fields = qw/time lot waf ts sstep machine product plnfile striping/;
    my %row;

    foreach $line (@lines) {
       @row{@fields} = split /,/, $line;

       if ($l eq $row{lot} && $w eq $row{waf}) {
            # do something...
       }
    }
}