$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;
                      }
                }
           }
      }