(my $break2 = $str2)=~ s/(length($str2)>30)/$1\n/mg;

You can't just use any code inside a regular expression and expect it to work.

I'd approach the problem like this:

sub break_word {
   my $str = shift;
   # break up $str into separate words,
   # and return the result
   ...
}

# search for all words longer than 30 characters:
s/(\S{31,})/ break_word($1) /eg;
[download]

$_ = 'might get it ---------------test-----------results----------.'
s/(\S{30})/$1 /g;
# $_ is now
#    'might get it ---------------test----------- results----------.'
[download]

I like this approach, I am trying to exclude the inserting of a break if the string in the sentence its a link starting with "http", it gets complicated I guess:

my $str2 = "Be careful what you wish for you just might get it http://
+www.perlmonks.com/?parent=943112;node_id=3333 ---------------test----
+-------resutls----------!";
(my $break3 = $str2)=~ s/([^http.*?\s+]\S{30})/$1 /g;
print "\n\n$break3\n\n";
[download]

I like this approach, I am trying to exclude the inserting of a break if the string in the sentence its a link starting with "http", it gets complicated I guess:

Um, are you trying to invent the syntax or guess?

This is your regex

use YAPE::Regex::Explain;
print YAPE::Regex::Explain ->new(
    qr/([^http.*?\s+]\S{30})/
)->explain;
__END__
The regular expression:

(?-imsx:([^http.*?\s+]\S{30}))

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [^http.*?\s+]            any character except: 'h', 't', 't',
                             'p', '.', '*', '?', whitespace (\n, \r,
                             \t, \f, and " "), '+'
----------------------------------------------------------------------
    \S{30}                   non-whitespace (all but \n, \r, \t, \f,
                             and " ") (30 times)
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
[download]

Neither approach is going to work

Try

s{(\S{30,}){
    my $ret = $1;
    if( $ret !~ /http/ ){
        $ret .= " ";
    }
    $ret;
}ge;
[download]

see also perlintro, perlretut, perlre#(?<!pattern)

Problem is, you end up adding a space even if the string is exactly 30 characters, resulting in a potential double-space.

use strict;
use warnings;

my $max = 5;
my $str = '123456789012';
$str =~ s/(\S{$max})(?=\S)/$1 /g;
print $str;
[download]

But what if you want to split into equal pieces?

use strict;
use warnings;

my $max = 5;
my $str = '123456789012';
$str =~ s/(\S\S{$max,})/mySplit($1)/eg;
print $str;

sub mySplit {
    my $s = $_[0];
    my ($n, $i, @p, @r);

    ### Calculate number of pieces
    $n = ceil (length($s) / $max);

    ### Calculate length of pieces
    for ($i = 0; $i < length $s; $i++) {
        $p[$i % $n]++;
    }
    ### Get pieces
    for (@p) {
        $s =~ s/(.{$_})//;
        push @r, $1;
    }
    return join ' ', @r;
}

sub ceil {
    return $_[0] == int $_[0] ? $_[0] : int ($_[0] + 1);
}
[download]