in Re: Geo::ShapeFile memory problem he was on the right track but maybe not as strong as needed. try this

 
$shapefile = Geo::ShapeFile->new ("tabblock2010_42_pophu");
$shapefile->caching(        shp                => 0); 
$shapefile->caching(        dbf                => 0); 
$shapefile->caching(        shx                => 0); 
$shapefile->caching(        shapes_in_area     => 0);
[download]

The dbf data is probably the smallest of them all.

Ive been playing, that worked for me. Mem usage is nice and flat now