perllearner,
I am not sure I understand completely, but I think the following does what you want:

print "Scan in Bar Code: ";
my $bar_code = <STDIN>;
chomp $bar_code;

if ( $bar_code ) {
    print "\n";
}
else {
    select(undef, undef, undef, .5);
    print "\r";
}
[download]

If this isn't what you want you are going to have to be more clear. You should also use CODE tags for your code so you get proper indentation.

Cheers - L~R