use warnings;
use strict;

while (<DATA>) 
{
    process_record ($_) if /\@user_info_start/;
}

sub process_record #include first and last line
{
   my $start_of_record = shift;
   my @userinfo;
   
   push @userinfo, $start_of_record;
   
   my $line;
   
   do { 
      $line =<DATA>;
      push @userinfo, $line;
   } until $line =~ /\@user_info_end/;
   
   print @userinfo; 
   print "\n";  
}   
   

=Prints

xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end

xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end

=cut

__DATA__
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end
d987sd66bd
xxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end
somebus here or blank lines? whatever
xxxxxxxxxxxxxxxxxxxxxxxxxxxx

##</code><code>##

use warnings;
use strict;

while (<DATA>) 
{
    process_record() if /\@user_info_start/;
}

sub process_record
{
  my $line;
  print $line while (defined ($line =<DATA>) and $line !~ /\@user_info_end/);
  print "\n";
}   
   

=Prints
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx

xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx

=cut

__DATA__
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end
d987sd66bd
xxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end
somebus here or blank lines? whatever
xxxxxxxxxxxxxxxxxxxxxxxxxxxx

##</code><code>##

use warnings;
use strict;

while (<DATA>) 
{
    process_record ($_) if /\@user_info_start/;
}

sub process_record #include first and last line
{
   my $start_of_record = shift;
     
   print $start_of_record;
   
   my $line;
   
   do { 
      $line =<DATA>;
      print $line;
   } until $line =~ /\@user_info_end/;

   print "\n";  
}   
   

=Prints

xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end

xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end

=cut

__DATA__
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end
d987sd66bd
xxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end
somebus here or blank lines? whatever
xxxxxxxxxxxxxxxxxxxxxxxxxxxx

##</code><code>##

use warnings;
use strict;

while (<DATA>) 
{
    process_record ($_) if /\@user_info_start/;
}

sub process_record # include first and last line
{
   my $start_of_record = shift;
     
   print $start_of_record;
   
   my $line;
   
   # a bit of strangeness caused by using <DATA> handle
   
   while (defined ($line=<DATA>) and $line !~ /\@user_info_end/)
   {
      print $line;
   }
   print $line;  #the last line of record

   print "\n";  
}   
   

=Prints

xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end

xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end

=cut

__DATA__
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : xxxxx
xxxx*@Filetype    : txt
xxxx*@Version       : 0001
xxxx*@Create_Date       : 20190407
xxxx*@Product       : xxxx
xxxx*@user_info_end
d987sd66bd
xxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxx
xxxx*@user_info_start
xxxx*@Title         : Mr
xxxx*@Username   : yy
xxxx*@Filetype    : txt
xxxx*@Version       : 0005
xxxx*@Create_Date       : 43
xxxx*@Product       : xxxx
xxxx*@user_info_end
somebus here or blank lines? whatever
xxxxxxxxxxxxxxxxxxxxxxxxxxxx