Also from Getopt::Long see the section 'Options with multiple values'

It says :-

Often it is useful to allow comma-separated lists of values as well as
multiple occurrences of the options. This is easy using Perl's split()
+ and
join() operators:

        GetOptions ("library=s" => \@libfiles);
        @libfiles = split(/,/,join(',',@libfiles));
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