$ guix build -f hello.scm
Backtrace:
In ice-9/boot-9.scm:
 157: 15 [catch #t #<catch-closure 1c94830> ...]
In unknown file:
   ?: 14 [apply-smob/1 #<catch-closure 1c94830>]
In ice-9/boot-9.scm:
  63: 13 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 432: 12 [eval # #]
In ice-9/boot-9.scm:
2401: 11 [save-module-excursion #<procedure 1ca4ca0 at ice-9/boot-9.scm:4045:3 ()>]
4050: 10 [#<procedure 1ca4ca0 at ice-9/boot-9.scm:4045:3 ()>]
1724: 9 [%start-stack load-stack ...]
1729: 8 [#<procedure 1cac6a8 ()>]
In unknown file:
   ?: 7 [primitive-load "/gnu/store/x4nfycabdkhvbcjdckva1fd1w8r5qqpm-guix-0.9.0/bin/.guix-real"]
In guix/ui.scm:
1173: 6 [run-guix-command build "-f" "hello.scm"]
In ice-9/boot-9.scm:
 157: 5 [catch srfi-34 #<procedure 2147330 at guix/ui.scm:411:2 ()> ...]
 157: 4 [catch system-error ...]
In guix/scripts/build.scm:
 507: 3 [#<procedure 2147340 at guix/scripts/build.scm:503:2 ()>]
 401: 2 [options->derivations #<build-daemon 256.14 2300d60> (# # # # ...)]
In srfi/srfi-1.scm:
 578: 1 [map #<procedure 2158fe0 at guix/scripts/build.scm:449:7 (expr)> #]
In guix/scripts/build.scm:
 431: 0 [object->argument #<unspecified>]

guix/scripts/build.scm:431:4: In procedure object->argument:
guix/scripts/build.scm:431:4: Throw to key `match-error' with args `("match" "no matching pattern" #<unspecified>)'.