Since I misinterpreted the question, I thought I'd offer another reply... $form would hold the data loaded in from file. An array called @data would hold the stuff you want to load into the Xs. The following hacky way of doing a format is suggested by perlform.

$form = <<"EOF";
XXXXX     XXXXX XXXX
  XX XX     XXXXX
X    XXXX    XXXX   XXX
EOF

@data = qw/one two three four five six seven eight nine ten/;

$form =~ s/\bX/\@/sg;
$form =~ s/X/</sg;
my $totalcount = 0;
my $format = "format STDOUT = \n";
foreach (split(/\n/,$form)) {
  $format .= $_."\n";
  (@c) = (m/([@<]+)/g);
  $format .= '$data['.$totalcount++.'],' for 0..$#c;
  $format =~ s/,$//s;
  $format .= "\n";
}
$format .= ".";

eval $format;
write;
[download]

This would produce this output:

one       two   thre
  fo fi     six
s    eigh    nine   ten

Hopefully having repented for my error, I hope that helps!

  -Adam