curl: (5) Couldn't resolve proxy 'hproxy.iitm.ac.in'

From the comments and your output of env, you still have some proxy variables set. Execute the following commands to unset them:

unset http_proxy
unset ftp_proxy
unset https_proxy

Double check that they've been removed by:

env | grep -i proxy

Now try your curl command.

You can temporarily bypass the proxy by using the --noproxy option, e.g.

curl -L https://get.rvm.io --noproxy | bash -s stable --ruby --autolibs=enable --auto-dotfiles

You may need to remove proxy settings in ~/.bashrc or ~/.profile or system wide(/etc/profile, /etc/bash.bashrc etc...). Also take a look at ~/.curlrc.

NOTE: if you are using GNOME Desktop Environment, you also need to unset the proxy in System Settings - Network.