use strict;

open OF1, ">var2_equal_to_3.txt";
open OF2, ">var2_not_equal_to_3.txt";
my ($flipflop, $flag, $prev);
while (<DATA>) {
    chomp;
    $flag = 1 if m/var2\s+=\s+3/i;
    $flipflop = /<rec\s+[0-9]+>/i .. /<\/rec\s+[0-9]+>/i;
    $prev = $_ if $flipflop == 1;
    if ($flag) {
        print OF1 "$prev\n"  if $flipflop == 2;
        print OF1 "$_\n";
    }else{
        print OF2 "$_\n";
    }
    $flag  = $prev = undef if $flipflop =~ /E0$/;
}

close OF1;
close OF2;
[download]

__DATA__
<Rec 1>
var2 = 5
some text
some text
some text
some text
</Rec 1>
<rec 2>
var2 = 3
some text
some text
some text
some text
some text
some text
some text
some text
</Rec 2>
<Rec 3>
var2 = 7
some text
some text
some text
some text
some text
some text
</Rec 3>
<rec 4>
var2 = 3
some text
some text
some text
some text
some text
some text
some text
some text
</Rec 4>
[download]