Can't locate IO/Pty.pm despte it being there

So I try and run my perl script using sudo and I get the following error:

Can't locate IO/Pty.pm in @INC (you may need to install the IO::Pty module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.20.2 /usr/local/share/perl/5.20.2 /usr/lib/x86_64-linux-gnu/perl5/5.20 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.20 /usr/share/perl/5.20 /usr/local/lib/site_perl .) at /usr/local/bin/myscript.pl line 4.

But if I try and install the missing perl module, the following happens:

cpan[2]> install IO::Pty.pm
IO::Pty is up to date (1.12).

I'm not sure what is happening since I clearly have IO/Pty.pm

via Chebli Mohamed