Actually, I like the fact that you don't clobber $_ . No reason to quote "$datafile". You could stand some diagnostics on the file open. Rather than having a 
while (1) { ... next if () ... last }

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structure, you could have used redo:

 LINE: {
        chomp($row = <$fh>) or last LINE;
        redo LINE if $key < $min;
        $done = 1 && return if ($key > $max);
      }

[download]
And you could generalize it a bit further, by making a general-purpose iterator maker that itself takes a CODE ref to call in the middle:

sub itter_maker {  # return a function that passes back data allowed b
+y the given predicate subroutine
  my $predicate = shift; #CODE ref
  my $done = 0;
  my $fh = IO::File->new($datafile) or die "can't open $datafile: $!\n
+";
  return(
    sub {
      return if $done;
      my (@data,$row,$key);
      my $found = 0;
      while(  ! $found  &&  ! $done  &&  defined( $row= <$fh> )  ) {
        chomp($row);
        ($found, $done) = $predicate->($row, \$key, \@data);
      }
      return ($key,\@data) if $found;
      return;
    });
}

[download]

update: changed to redo, fixed predicate call syntax.
update2: incorporated tye's suggestion, thanks!

In reply to Re: Closures as Itterators by bikeNomad
in thread Closures as Itterators by blakem

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