Well, your map-code seems perfectly OK to me. No problems there, unless you have non-numeric data. You could add a test for that.

Your code can easily be written in grep, but it's less efficient, as grep just is slower than map.

Maybe you can increase your understanding of map and grep by looking at them as filters. You have a list, put them in map, and you return something different. In this respect grep is more like a seeve. In a diagram:

             ____________
<list> ---> | filter-code| --> <modified list>
             ------------
[download]

Than you flip the picture around, and you have a pretty cood idea of what map does. It only reads right-to-left.

If you get this, you can start playing around with it. For example, take multi-column data, split them, and count the number of ones in the 3th column in a running fashion.

@n = map{ split; 
          $count += $_[2] =~ tr/1/1/;
          print join "\t", $idx++, $_[2], $count, $count/ $idx;
          print "\n";
          $count;
        }
    <DATA>;

__DATA__
1 2 31 4
100 5 91111111111111111 1
3 4 -6 1
8888888 8 191 1
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just to mention some funny useless stuff.

I hope this helps to see the power of map. The next level than is the Schwartzian transformation.

Have fun with it,

Jeroen
"We are not alone"(FZ)