G'day mtorba,

Welcome to the Monastery.

This sounds like a job for the Range Operator. Perhaps something like this:

#!/usr/bin/env perl

use strict;
use warnings;

while (<DATA>) {
    if (/^regex1/ .. /^regex3/) {
        last if /^regex3/;
        print;
    }
}


__DATA__
PRE REGEX LINES
regex1 - grab general informations about regex1
grab more informations on this line about regex1
regex2 - grab general informations about regex2
grab more informations on this line about regex2
regex3 - grab general informations about regex3
grab more informations on this line about regex3
POST REGEX LINES
[download]

Output:

regex1 - grab general informations about regex1
grab more informations on this line about regex1
regex2 - grab general informations about regex2
grab more informations on this line about regex2
[download]

While I appreciate this is your first post, it is lacking in several areas (including runnable code, actual output, expected output, etc.) and responses will reflect this. A better question will get you a better answer. Please see "How do I post a question effectively?" for ways to improve future posts.