#!/usr/bin/perl -w
use strict;

my $line=();
while (<DATA>)
{
   next if /^\s*$/;
   
   # $flag is not necessary here, it is there to
   # show the return value of this triple dot operator
   # for /start/.../end/
   
   if ( my $flag = ( /start /.../end/) )
   {
      s/end.*/end/s;
      s/.*?start/start/;
      s/\n//;
      $line .= "$_";
      # print "$flag\n"; #interesting 1, 2, 3E0 etc....

      if ( $_=~ m/end$/ )
      {
         print "OUT:$line\n";
         $line =();
      }
   }
}

#Prints:
#OUT:start 1asdasd asdasdasd asdasdas end
#OUT:start 2as asdas dasdasdad asdasddas end
#OUT:start 3asdsadsdasddasds sdasdas asdasdasdasd asdasdsa asdasd asdasdasd and this is an evenlonger way to stop a line with )&)9867 some end
#OUT:start 4another line end

__DATA__
asdasd start 1asdasd asdasdasd asdasdas end asdasdas

adasdas start 2as asdas dasdasdad asdasddas end qweqwe

asdasd start 3asdsadsdasddasds sdasdas asdasdasdasd asdasdsa 
asdasd asdasdasd and this is an even
longer way to stop a line with )&)9867 some end garbage

start 4another line end abc