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

my @array;
while( <DATA> ) {
  @array = (@array,$_);
  if (/<sep>/) {
    print join '',sort {$a <=> $b} @array;
    print "<sep>\n";
    @array=();
  }
}
print join '',sort {$a <=> $b} @array;
__DATA__
<sep>
22
1
3
<sep>
4
2
44