Thanks to all you monks for the precious suggestions you gave to me!
I know my code is still terrible!! 
#!perl

use strict;
use warnings;

&changemyself();
sub changemyself{
  my $new_value = 10;
  my $data=6666666666666;   #next time this value will be 10

 open (COPIA, ">copia");
 open (PROG, "+>>$0");
 seek (PROG, 0, 0);         #I don't know why but it's NECESSARY!

 while (<PROG>)
 {
   s/^(  my .data\s*=\s*)\d+(\s*;)/$1.$new_value.$2/e;
   print COPIA;
 }
 close (PROG);              #
 close (COPIA);             #
                            #   the terrible imitation 
                            #     of the
 open (COPIA, "<copia");    #   three cards game
 open (PROG, ">$0");        #
 while (<COPIA>){print PROG}#
 close (PROG);              #
 close (COPIA);             #
 unlink ("copia");          #
}

[download]
Special thank to Helter!
greetings from roma, lor*
PS I never noticed the +>> operator!!! l*

In reply to Re: Re: Re: substitution in $0 by Discipulus
in thread substitution in $0 by Discipulus

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.