% perl -wle '$x = "1e-149"; print $x + "2e-149"'           
3e-149
% perl -wle '$hash{ x } = "1e-149"; print $hash{ x } + "2e-149"'
3e-149
% perl -wle '$hash{ x } = "1e-149"; print $hash{ x } + "2e-36"' 
2e-36