sub check_quota {
   my $hash_ref=shift;
   my (@users,@list);
   my %hash;
   #print Dumper($hash_ref);

   for my $user (keys %$hash_ref) {
      push(@users, $user);
   }

   my @repq_h=grep {
      #print $_,"\n";
      if($_ =~ m{^([A-Za-z0-9]+)}) {
         my $word=$1;
         push(@{$hash{$word}},$_);
         grep $word,@users;
      }
   } qx{repquota -a};
   print Dumper(\@repq_h);
}

# adjust path to executable
my $cmd = '/bin/repquota -a';
# execute command and fetch its output in @output
my @output = qx~ $cmd ~;
# check $? if $cmd executed successfully

root@homer:~# repquota -a
*** Report for user quotas on device /dev/mapper/lvm--raid--1-lv1
Block grace time: 7days; Inode grace time: 7days
                        Block limits                File limits
User            used    soft    hard  grace    used  soft  hard  grace
----------------------------------------------------------------------
root      --  192252       0       0              5     0     0       
user1     --       4 18874368 20971520              1     0     0       
user2      --    2440 18874368 20971520              7     0     0       
user3  --       4 18874368 20971520              1     0     0       
user4    --  111764 18874368 20971520           1060     0     0         


root@homer:~# 

my @output = `repquota -a`;
{
        my    $status = $? >> 8;
        local $"      = "\n"; # "
        die "'repquota -a' returned bad status: $status\nOutput: @output" if $status;
}

splice( @output, 0, 5 );

my @user = grep { defined $_ } map { /^(\S+)/ ? $1 : undef } @output;

# vorrausgesetzt: my $passwd = parse_passwd( '/etc/passwd' );
@user = grep { exists $passwd->{$_} } @user;