title: bash command expansion
body: <p>The following bash command substitution does not work as I thought.</p>
  
  <pre><code>echo $TMUX_$(echo 1)
  </code></pre>
  
  <p>only prints 1 and I am expecting the value of the variable <code>$TMUX_1</code>.I also tried:</p>
  
  <pre><code>echo ${TMUX_$(echo 1)}
  -bash: ${TMUXPWD_$(echo 1)}: bad substitution
  </code></pre>
  
  <p>Any suggestions ?</p>