use strict;
use Data::Dumper;
use Carp;

my @nar = (
              ['fact 1 - ParamGrp1', 'foo', 'bar'],
              ['fact 1 - ParamGrp2', 'qux', 'bom'],
              ['fact 1 - ParamGrp1', 'fuu', 'gong'],
              ['fact 2 - ParamGrp1', 'fiu', 'ging'],
);

    my %hash;
    my %param_hash;
    foreach my $nar (@nar) {
        my ( $cwd, $prm ) = split( " - ", $nar->[0] );
        my @rest = @{$nar}[ 1 .. @{$nar} - 1 ];
        push @{ $param_hash{$prm} }, [@rest];
            $hash{$cwd} = {%param_hash};
    }

print Dumper \%hash ;