C:\Users\David\Documents\3D_Printer\Slic3r>perl Build.PL
cpanm was not found. Please install it before running this script.

There are several ways to install cpanm, try one of these:

    apt-get install cpanminus
    curl -L http://cpanmin.us | perl - --sudo App::cpanminus
    cpan App::cpanminus

If it is installed in a non-standard location you can do:

    CPANM=/path/to/cpanm perl Build.PL

C:\Users\David\Documents\3D_Printer\Slic3r>