It was added in version 2.35, released on 28-Apr-2005:

Changes in version 2.35
-----------------------
:
* Options can take multiple values at once. E.g.,

    --coordinates 52.2 16.4 --rgbcolor 255 255 149

  To handle the above command line, the following call to GetOptions
  can be used:

    GetOptions('coordinates=f{2}' => \@coor, 'rgbcolor=i{3}' => \@colo
+r);

  You can specify the minimum and maximum number of values desired.
  The syntax for this is similar to that of regular expression
  patterns: { min , max }.
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I wasn't even considering people using that old a version. You're probably right.