Bah! Looks like printf won't do centering. Have to calculate the space by hand. (As another responder posted...)

use strict;
 
my @lines = <DATA>;
my $maxsize = 0;
map {chomp; $maxsize = ($maxsize>length)?($maxsize):(length)} @lines;
print "max size: $maxsize\n";
my $windowSize = $maxsize +4;
my $bar = '*' x $windowSize . "\n";
 
foreach (@lines)
{
  # calculate space between this line and window border
  my $space = $maxsize - length($_);
 
  # determine if the space is an odd or even number
  my $odd = $space%2;
 
  # half the space will go on the left, half will
  # go on the left (plus one if it was odd).
  my $spacer = int($space/2);
 
  print($bar);
  print('* ' . ' ' x $spacer . $_ . ' ' x ($spacer + $odd) . " *\n");
  print($bar);
}
 
 
__DATA__
some lines
that are of different sizes
Some small
really small.
----------------some large---------------------
--------------------------------------------------some huge-----------
+---------------------------------------
...
[download]