$myPolygons = 

"<tag>
<name>A</name>
     <points>-1.1,2,0 -3.1,4,0 -5.1,6,0 -7.1,8,0 1,2,0</points>
<name>C</name>
     <points>9,-8.1,0 7,-6.1,0 5,-4.1,0 3,-2.1,0 9,-8.1,0</points>
</tag>";

while ($myFile =~ m{<tag>(.*?)</tag>}gs)
     {
     $tag = $1;
     if ($tag =~ m{<name>(.*?)</name>}gs)
          {
          $name = $1;
	  if ($tag =~ m{<points>(.*)</points>}g)
	       {
	       $points = $1;
	       while ($points =~ m{\G(-?\d*\.?\d*),0*\s*}gs)
                      {
                      push @{$points_by_name{$name}}, $1;
                      }
                }
           }
      }
     

##</code><code>##

@_ = ($x0, $y0, $x1, $y1, $x2, $y2, $x3, $y3)

##</code><code>##

$x0, $y0, $x1, $y1

##</code><code>##

@{$points_by_name{$key}}[0..3];
@{$points_by_name{$key}}[2..5];
@{$points_by_name{$key}}[4..7];
@{$points_by_name{$key}}[6..9];

##</code><code>##

foreach my $key (keys %points_by_name)
	{
	foreach (@{$points_by_name{$key}}
		{
		for (my $i=0; $i<=$#{$points_by_name{$key}} $i+=2)
			{
			sub(@{$points_by_name{$key}}[$i..$i+3], $x2, $y2, $x3, $y3)
			}
		}
	}

##</code><code>##

foreach my $key (keys %other_hash)
	{
	foreach (@{$other_hash{$key}}
		{
		for (my $i=0; $i<=$#{$points_by_name{$key}} $i+=2)
			{
			my @temp = @{$other_hash{$key}}[$i..$i+3]
			foreach (@temp)
				{
				sub($x0, $y0, $x1, $y1, @temp)
				}
			}
		}
	}