#!/usr/bin/perl -w
use strict;
my $x = 3;
for(1..3){
    my $y = $x;
    $y++;
    $x -= $y;
}

[download]

The above little programme, if I put an acton on line 6 ($y++) the action occurs at line 6, line 7 then at line 5 where it is invalid ($y not defined)

To illustrate here is my session in the debugger...

  DB<3> a 6 print ("\$y $y\n")
  DB<4> n
  DB<4> 
  DB<4> 
$y 3
  DB<4> 
$y 4
  DB<4> 
Use of uninitialized value $y in concatenation (.) or string at (eval 
+9)[/usr/share/perl/5.18/perl5db.pl:732] line 1.
 at (eval 9)[/usr/share/perl/5.18/perl5db.pl:732] line 1.
    eval 'no strict; ($@, $!, $^E, $,, $/, $\\, $^W) = @DB::saved;pack
+age main; print ("\\$y $y\\n");
' called at /usr/share/perl/5.18/perl5db.pl line 732
    DB::eval called at /usr/share/perl/5.18/perl5db.pl line 2661
    DB::DB called at test.pl line 5
$y 
  DB<4>

[download]

Clearly I misunderstand the manual. How do I do an action so it happens on only one line?

In reply to Debugger actions: On which lines? by worik

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.