add env fallback example (nushell#1226)

* [placeholder] How can you use a variable fallback? * fix placeholder fallback --------- Co-authored-by: Darren Schroeder <[email protected]>
kubouch · Feb 3, 2024 · 2a0862e · 2a0862e
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commit 2a0862e
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diff --git a/book/coming_from_bash.md b/book/coming_from_bash.md
@@ -55,6 +55,7 @@ Note: this table assumes Nu 0.60.0 or later.
 | `FOO=BAR ./bin`                      | `FOO=BAR ./bin`                                               | Update environment temporarily                                    |
 | `export FOO=BAR`                     | `$env.FOO = BAR`                                              | Set environment variable for current session                      |
 | `echo $FOO`                          | `$env.FOO`                                                    | Use environment variables                                         |
+| `echo ${FOO:-fallback}`              | `$env.FOO? | default "ABC"`                                   | Use a fallback in place of an unset variable                      |
 | `unset FOO`                          | `hide-env FOO`                                                | Unset environment variable for current session                    |
 | `alias s="git status -sb"`           | `alias s = git status -sb`                                    | Define an alias temporarily                                       |
 | `type FOO`                           | `which FOO`                                                   | Display information about a command (builtin, alias, or executable) |