It is a one-liner, because I wouldn't bother filing it as another script.

####################################

Here's your code reformatted:

About passing the input file on the command line, it would be an interesting issue since I would then need to use the <STDIN> diamond to ask for the quantities. If not, it would mess with the previous <> input ...

#!/your/perl/here

use strict;
use warnings;

while (<>)
{ 
    print "one: $_";
}

print "\n\n: now reading from STDIN: \n\n";

print "Enter data: ";
while (<>)
{ 
    print "two: $_";
    print "Enter data: ";
}
[download]

I'm suggesting that some medications come in different pill concentrations, and you might save money by shopping around. And you might program that by using a file for the prescribed doses, and another file for the concentration/price tables.

Now, I've left something out. You could do this by passing 2 files on the command line, and making judicious use of the continue and eof elements. Just check out eof for more details.

Cheers,