man/man1/:.1

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NAME            :  --  place a label
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SYNOPSIS        :\b_ [ label ]
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DESCRIPTION     :\b_
does nothing.  Its only function is to place
a label for the goto\b\b\b\b____ command.  :\b_ is a command
so the Shell doesn't have to be fixed to ignore lines with
:'s.
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FILES           --
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SEE ALSO        goto(I)
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DIAGNOSTICS     --
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BUGS            --