Melly,
Salutations from vacation land. This could be way off base so forgive me. Assuming that individual records are not that large (just the file), then a user controlled buffer should work fine.

#!/usr/bin/perl
use strict;
use warnings;

my $file = $ARGV[0] || 'export.dat';
open(my $fh, '<', $file) or die "Unable to open '$file' for reading: $
+!";
my @buffer;
while (<$fh>) {
    if (/^1(\d+.*)/) {                    # Start of new record
        output_data(@buffer) if @buffer;  # process last record if not
+ first
        @buffer = $1;                     # put new line in buffer
    }
    else {
        push @buffer, $_;                 # Add line to buffer
    }
}
output_data(@buffer) if @buffer;          # Process last record if pre
+sent

sub output_data {}
[download]

I am sure you will have to tweak it. Update: I just realized writing to a temporary file was important. Oh well.