% exec my-echo.cmd {test&whoami}
  test
  mylogin
% exec my-echo.cmd "ENV X:%X%"
  ENV X: CONTENT OF X
.CE
The following formatting is automatically performed on any
argument item:
.IP \(bu 3
Avoid subprogram execution:
argument item to avoid subprogram execution:
Any special character argument containing a special character (\fB&\fR, \fB|\fR,
\fB^\fR, \fB<\fR, \fB>\fR, \fB!\fR, \fB(\fR, \fB)\fR, \fB(\fR, \fB%\fR)
is automatically enclosed in quotes (\fB"\fR). Any data quote is escaped by
insertion of backslash characters.
.IP \(bu 3
Avoid environment variable replacement:
Any appearence of environment variable reference (\fB%\fR) is individually quoted
.PP
The automatic resolving of environment variables using "\fB%var%\fR" is critical,
but has more use than danger and is not escaped.
by \fB"\fR.
.PP
TCL 8.6.10 refined this quoting by adding quoting for data quotes and individual
quoting of "\fB%\fR".
This may break present scripts which rely on the replacement functionality of
environment variables.
Thus, the individual quoting of "\fB%\fR" was removed in TCL 8.6.14, as environment
variables are seen more helpful than a problem.
A solution with command parameters is envisaged for a future release of TCL.
.RE
.PP
The Tk console text widget does not provide real standard IO capabilities.
Under Tk, when redirecting from standard input, all applications will see an
immediate end-of-file; information redirected to standard output or standard
error will be discarded.