This is true for Bash scripts, but not for POSIX shell scripts.

% /bin/sh --version
GNU bash, version 3.2.57(1)-release (arm64-apple-darwin26)
Copyright (C) 2007 Free Software Foundation, Inc.

~% /bin/sh <<EOF
heredoc> alias x=echo
heredoc> x hello
heredoc> EOF
hello

(Bash runs in POSIX mode when invoked as sh)

score 1 · canonical