newenvironment{foo}%
{%
%
  newcommandbara{}%
  newcommandbarb[1]{%
    renewcommandbara{##1}%
    typeout{FIRST}%
    typeout{##1}{bara}%
  }%

  newenvironment{baz}%
  {%
    begin{figure}[!h]%
    centering%
    begin{tikzpicture}{scale=1}%
  }%
  {%
    typeout{SECOND}%
    typeout{bara}%
    end{tikzpicture}%
    typeout{bara}%
    caption{bara}%
    end{figure}%
  }%
}%
{}%

begin{foo}
  begin{baz}
    bara{abc}
  end{baz}
end{foo}

FIRST
abc
SECOND
abc
[blank]

FIRST
abc
SECOND
abc
abc

documentclass{article}
makeatletter
newenvironment{foo}%
{%
%
  newcommand@bar{}%
  renewcommandbar[1]{%
    renewcommand@bar{##1}%
    typeout{FIRST}%
    typeout{##1}{@bar}%
  }%
%
  newenvironment{baz}%
  {%
  }%
  {%
    typeout{SECOND}%
    typeout{@bar}%
  }%
}%
{}%
makeatother

begin{document}
begin{foo}
  begin{baz}
    bar{abc}
  end{baz}
end{foo}
end{document}

% latex tmp.tex
[snip]
FIRST
abc
SECOND
abc
[snip]
Output written on tmp.pdf (1 page, 11670 bytes).
Transcript written on tmp.log.