Escape <variable> in cheat files

Is your feature request related to a problem? Please describe.

# build default.nix
nix-build -E 'with import <nixpkgs> {} ; callPackage ./default.nix {}'

this line things of nixpkgs> as a variable, but it actually should stay `.

Describe the solution you'd like

Best we to escapt <nixpkgs> some how.

Describe alternatives you've considered

currently I ship around it, by defining

$ nixpkgs: echo "<nixpkgs>"