Almost 3 years later, I actually tried this. It does not appear to work: execution does not stop when the variable changes value, and the L command does not show the watchpoint. My Perl version is 5.8.8; that might be important.

You're right, the solution is pretty simple. Create a ref to the variable of interest and make the watchpoint the dereferenced value. This has the very slight disadvantage of having to wait until the variable of interest has been created, but avoiding the maddening interruptions is wonderful!

Program slightly modified for demonstration purposes:

use strict;

my $t = 14;
print "$t\n";
$t = 15;
print "$t\n";
blah();
print "$t\n";

sub blah {
  my $t = 42;
  print "$t\n";
}

[download]

Debug session - Was:

  DB<1> w $t
  DB<2> c
Watchpoint 0:   $t changed:
    old value:  ''
    new value:  '14'
main::(dbt.pl:4):       print "$t\n";
  DB<2> c
14
Watchpoint 0:   $t changed:
    old value:  '14'
    new value:  '15'
main::(dbt.pl:6):       print "$t\n";
  DB<2> c
15
Watchpoint 0:   $t changed:   <<<<< the bane of my existence 
    old value:  '15'
    new value:  '42'
main::blah(dbt.pl:12):    print "$t\n";
  DB<2> c
42
Watchpoint 0:   $t changed:  <<<<< just more bane
    old value:  '42'
    new value:  '15'
main::(dbt.pl:8):       print "$t\n";
  DB<2> c
15
Watchpoint 0:   $t changed:
    old value:  '15'
    new value:  ''
Debugged program terminated.

[download]

Now:

  DB<1> w $t
  DB<2> c
Watchpoint 0:   $t changed:
    old value:  ''
    new value:  '14'
main::(dbt.pl:4):       print "$t\n";
  DB<2> W $t
  DB<3> $z=\$t
  DB<4> w $$z
  DB<5> c
14
Watchpoint 0:   $$z changed:
    old value:  '14'
    new value:  '15'
main::(dbt.pl:6):       print "$t\n";
  DB<5> c
15
42
15
Watchpoint 0:   $$z changed:
    old value:  '15'
    new value:  ''
Debugged program terminated.

[download]
But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us. Romans 5:8 (NASB)

In reply to Re^2: Debugger Questions - Variable Scope (source++) by GotToBTru
in thread Debugger Questions - Variable Scope by GotToBTru

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.