Local versions of names can be created that overshadow the protected version.
>

$\mathbf{local}\mathrm{length}\u22540.001$

>

${\mathrm{length}}^{2}$

${1.}{\times}{{10}}^{{\mathrm{6}}}$
 (9) 
The original procedure is still available as :length.
>

$:\mathrm{length}\left(''abc''\right)$

The imaginary unit is special. When overridden with a local, the global version can be accessed via _I.
$\left[\begin{array}{cc}{1}& {0}\\ {0}& {1}\end{array}\right]$
 (11) 
$\left[\begin{array}{cc}{1}& {0}\\ {0}& {1}\end{array}\right]$
 (12) 
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$\mathrm{interface}\left(\mathrm{imaginaryunit}\right)$

To reset the imaginary unit after declaring it local, use the unbind command.
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$\mathrm{unbind}\left('\mathrm{I}'\right)$

>

$\mathrm{interface}\left(\mathrm{imaginaryunit}=\mathrm{I}\right)$
