You're working on a system with limited resources, I installed it here on a system with the same amount of RAM as the Raspberry pi (the 1GB models anyway :), without any issues. If your pi is currently doing lots of other work consider trying to use cpanm to install modules, it's lighter on system resources and faster:

cpanm Number::Format
[download]

A while ago I detailed some tweaks to make better use of resources on the Raspberry Pi, some of which may still be applicable.

Update: added clarification of pi model.