It doesn't change anything on perl 5.20.1. I tried:

sub calc {
  my $t = $scale;
  $xmax = $x * $t;
  $ymax = $y * $t;
  $results = sprintf("Calculated X-max=%8.4f, Y-Max=%8.4f",$xmax,$ymax
+);
  print " $x , $y , $scale , $t , $xmax , $ymax\n";
  print "'$x','$y','$scale','$t','$xmax','$ymax'\n";
  print join(', ',hexify($x),hexify($y),hexify($scale),hexify($t),hexi
+fy($xmax),hexify($ymax))."\n\n";
}
sub hexify {
  my $s = shift;
  $s =~ s/(.)/sprintf("%x ",ord($1))/eg;
  return $s;
}
[download]

The values all print out the same with the incorrect products. No extra characters whether I print $x or '$x' or the hexified version

However, if I change the second line to: my $t = $scale.' '; it works!

I can't really call it solved, since I don't know why it's doing this. But at least, I have a work-around to make my main program behave.