When I have numerical data, I like to store it as such in whatever database I'm using, so that I can take advantage of numeric database functions if I need to. But when it comes time to manipulate, compare or display the data, Perl doesn't really care -- it is all just a scalar. I often use sprintf to format data that I select from a database but need to have in a particular format:

  use strict;
  use warnings;
  use DBI;
  # assuming $dbh is a connected database handle
  my $result_ref = $dbh->selectall_arrayref("select field1, field2 fro
+m testtable");
  if ($DBI::errstr) {
    print "An error was encountered in retrieving data : $DBI::errstr"
+;
  }
  foreach my $thisrow (@$result_ref) {
    my $field1 = sprintf "%06d",$thisrow->[0];
    my $field2 = $thisrow->[1];
    # do whatever you need to do with those values
  }
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Of course, many relational databases also have internal formatting instructions (e.g. Oracle's lpad or rpad) which can take care of this for you as well.