I updated to fix that, thanks for pointing it out. It had to do with echo printing the command with your backspace characters escaped. See if you can break it now, it's interesting how many weird cases exist in tty's.
This script, for example looks sort of innocuous when run through your tool because it's not obvious the HEREDOC is going to the stdin of a Perl interpreter. Your tool shows them like they are two separate things that don't do much by themselves.
Looking at the script itself, it's more obvious.
#!/bin/sh
cat<<'EOF'|perl -nE'BEGIN{shift(@ARGV)}s#(.*)#$1#ee' /dev/null
say "hello"; #arbitrary perl code
EOF