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+## In POSIX sh, naming functions outside [a-zA-Z_][a-zA-Z0-9_]* is undefined.
+
+### Problematic code:
+
+```sh
+#!/bin/sh
+run-tests() {
+  make test
+}
+```
+
+### Correct code:
+
+```sh
+#!/bin/sh
+run_tests() {
+  make test
+}
+```
+
+### Rationale:
+
+Your script uses a shell feature not supported by the shebang. Either rewrite the script to be portable, or change the shebang to explicitly require a shell like Bash.
+
+In this case, you can rename your functions to follow the same naming requirements as variables, as these are the only names guaranteed to be valid function names in POSIX.
+
+### Exceptions:
+
+None
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!
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