$ perl -Mstrict -Mwarnings -MData::Dumper -e '
sub groupsOf (&$@);

open my $inFH, q{<}, \ <<EOD or die $!;
a
b
c
d
e
f
g
h
EOD

my @arr;
push @arr, groupsOf { chomp @_; [ @_ ] } 3, <$inFH>;

sub groupsOf (&$@)
{
    my $rcToRun  = shift;
    my $groupsOf = shift;

    my $rcDoIt;
    $rcDoIt = sub
       {
           $rcToRun->(
              map shift, 1 .. ( @_ < $groupsOf ? @_ : $groupsOf )
              ),
           @_ ? &$rcDoIt : ();
       };

    &$rcDoIt;
}

print Data::Dumper->Dumpxs( [ \ @arr ], [ qw{ *arr } ] );'
@arr = (
         [
           'a',
           'b',
           'c'
         ],
         [
           'd',
           'e',
           'f'
         ],
         [
           'g',
           'h'
         ]
       );
$