#!/usr/bin/perl -w

use strict;
my $block;
while (<DATA>) {
   if (!/^\n/) {
      $block .= $_;
   }else{
      process($block);
      undef($block);
   }
}
process($block) if ($block);

sub process {
   my $info = shift;
   print "\n",$info if ($info);
}

__DATA__
USER 1
LOGIN date
MORE info
MORE info

USER 2
LOGIN date
MORE info
MORE info