How to use --bind "enter:become(nvim {+}) in environment variable FZF_CTRL_T_OPTS?

[sunbearc22]

When I run fzf --multi --bind 'enter:become(vim {+})' from the command-line, nvim runs and is able to open the file when i press Enter .

But when I put these options in environmental variable, e.g.

export FZF_CTRL_T_OPTS='
  --style minimal --layout reverse
  --border --padding 1,2 --height 100%
  --preview "fzf-preview.sh {}"
  --multi --bind "enter:become(nvim {+})"
'

after pressing Ctrl+T and pressing Enter, nvim does not appear and neither does the document. The terminal hangs and I have to press Ctrl+C to return the command-line prompt.

So how do I use --multi --bind "enter:become(nvim {+})" in my options so than nvim can open the file that I had selected in fzf?

[sunbearc22]

I discovered that by replacing --bind "enter:become(nvim {+})" with --bind "enter:execute(nvim {+})+abort", the above environment variable worked.

But according to documentation:

become(...) is similar to execute(...)/execute-silent(...) described above, but instead of executing the command and coming back to fzf on complete, it turns fzf into a new process for the command.

I don't understand why --bind 'enter:become(vim {+})' work from the command-line and not when it is used in an environment variable. Can someone explain why? Also, please explain why "enter:execute(nvim {+})+abort" works in an environment variable. Thank you.