use strict;
use warnings;
use Getopt::Long;

# fake populate ARGV
my $sLine= <<EOF;
-cmdline_option REG1=value1.1, value1.2, value1.3, value1.4
-cmdline_option REG2=value2.1, value2.2, value2.3, value2.4
-cmdline_option REG3=value3.1, value3.2, value3.3, value3.4
EOF

@ARGV = split(/\s+/, $sLine);

sub makeKeyValuePairsIntoHoA;

# ====================================================
# parse the command line
# ====================================================

my @aCmdLineOpts;
GetOptions('-cmdline_option=s@{0,}' => \@aCmdLineOpts);
my $hCmdline = makeKeyValuePairsIntoHoA(\@aCmdLineOpts);



# see results
foreach my $k (sort keys %$hCmdline) {
  my $v = $hCmdline->{$k};
  print "$k:<@$v>\n";
}

# ====================================================
# subroutine for making key-value pairs into an HoA
# ====================================================
sub makeKeyValuePairsIntoHoA {
  my ($aValues) = @_;
  # consolidate arguments so that all the
  # values belonging to REG1= are in a single
  # comma delimited list without spaces.

  my $sAllInOne = join(' ', @$aValues);
  $sAllInOne =~ s/\s*,\s*/,/g;

  # split into key-value pairs on whitespace
  my @aKeyValuePairs = split(/\s+/, $sAllInOne);
  my %hKeyValuePairs = map
    { my ($k,$v) = /(\w+)+=(.*)/;
      $k => [ split(/,/, $v) ]
    } @aKeyValuePairs;

  return \%hKeyValuePairs;
}