(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;
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