use Linux::Fuser;

my $fuser = Linux::Fuser->new();
my @procs = $fuser->fuser($file) or die $!;
my $ruser = (); 

foreach my $proc (@procs) {
   my $pid = $proc->pid;

   open my $fh, '<', "/proc/$pid/environ" or die $!; 
   my $env = do { local $/; <$fh> };
   foreach my $pair (split /\0/, $env) {
      next unless $pair =~ /^\s*REMOTE_USER=(.+)/;
      $ruser .= "$1<br/>";
   }   
}