I agree with Your Mother that this is probably not a good idea. If you really need it, here is a way to do it.

C:\Users\Bill\forums\monks>type perl_script.pl
use strict;
use warnings;
use Getopt::Long;

my $temp;
GetOptions("flag:s" => \$temp);
my @flags = split /,/, $temp ;
print join(' ', @flags,), '     ', scalar @flags, " strings\n";


C:\Users\Bill\forums\monks>.\perl_script.pl --flag
     0 strings

C:\Users\Bill\forums\monks>.\perl_script.pl --flag a
a     1 strings

C:\Users\Bill\forums\monks>.\perl_script.pl --flag a,b,c
a b c     3 strings
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