The same holds for evaluated strings that contain subroutines, or
which are currently being executed. The $filename for C<eval>ed strings
-looks like C<(eval 34)> or C<(re_eval 19)>.
+looks like C<(eval 34)> or C<(re_eval 19)>.
=item *
contents of this variable are treated as if they were the argument
of an C<o ...> debugger command (q.v. in L<perldebug/Options>).
-=head3 Debugger internal variables
+=head3 Debugger Internal Variables
In addition to the file and subroutine-related variables mentioned above,
the debugger also maintains various magical internal variables.
=item *
-C<%DB::dbline>, is an alias for C<%{"::_<current_file"}>, which
+C<%DB::dbline> is an alias for C<%{"::_<current_file"}>, which
contains breakpoints and actions keyed by line number in
the currently-selected file, either explicitly chosen with the
debugger's C<f> command, or implicitly by flow of execution.
=back
-=head3 Debugger customization functions
+=head3 Debugger Customization Functions
Some functions are provided to simplify customization.
By way of demonstration, we present below a laborious listing
resulting from setting your C<PERLDB_OPTS> environment variable to
the value C<f=n N>, and running I<perl -d -V> from the command line.
-Examples use various values of C<n> are shown to give you a feel
-for the difference between settings. Long those it may be, this
+Examples using various values of C<n> are shown to give you a feel
+for the difference between settings. Long though it may be, this
is not a complete listing, but only excerpts.
=over 4
is printed with proper indentation.
-=head1 Debugging regular expressions
+=head1 Debugging Regular Expressions
There are two ways to enable debugging output for regular expressions.
compile time and run time. Since Perl 5.9.5, this pragma is lexically
scoped.
-=head2 Compile-time output
+=head2 Compile-time Output
The debugging output at compile time looks like this:
=item C<anchored(TYPE)>
-If the pattern may match only at a handful of places, (with C<TYPE>
+If the pattern may match only at a handful of places, with C<TYPE>
being C<BOL>, C<MBOL>, or C<GPOS>. See the table below.
=back
C< >I<id>: I<TYPE> I<OPTIONAL-INFO> (I<next-id>)
-=head2 Types of nodes
+=head2 Types of Nodes
Here are the possible types, with short descriptions:
IFMATCH off 1 2 Succeeds if the following matches.
UNLESSM off 1 2 Fails if the following matches.
SUSPEND off 1 1 "Independent" sub-regex.
- IFTHEN off 1 1 Switch, should be preceded by switcher .
+ IFTHEN off 1 1 Switch, should be preceded by switcher.
GROUPP num 1 Whether the group matched.
# Support for long regex
# This is not used yet
RENUM off 1 1 Group with independently numbered parens.
- # This is not really a node, but an optimized away piece of a "long" node.
+ # This is not really a node, but an optimized-away piece of a "long" node.
# To simplify debugging output, we mark it as if it were a node
OPTIMIZED off Placeholder for dump.
C<0[0]> items indicate that there is no corresponding node.
-=head2 Run-time output
+=head2 Run-time Output
First of all, when doing a match, one may get no run-time output even
if debugging is enabled. This means that the regex engine was never
The I<TYPE> info is indented with respect to the backtracking level.
Other incidental information appears interspersed within.
-=head1 Debugging Perl memory usage
+=head1 Debugging Perl Memory Usage
Perl is a profligate wastrel when it comes to memory use. There
is a saying that to estimate memory usage of Perl, assume a reasonable
The switch was used to track Perl's memory allocations and possible
memory leaks. These days the use of malloc debugging tools like
F<Purify> or F<valgrind> is suggested instead. See also
-L<perlhack/PERL_MEM_LOG>.
+L<perlhacktips/PERL_MEM_LOG>.
One way to find out how much memory is being used by Perl data
structures is to install the Devel::Size module from CPAN: it gives
and total_size().
If Perl has been compiled using Perl's malloc you can analyze Perl
-memory usage by setting the $ENV{PERL_DEBUG_MSTATS}.
+memory usage by setting $ENV{PERL_DEBUG_MSTATS}.
=head2 Using C<$ENV{PERL_DEBUG_MSTATS}>
In a Perl built for debugging, some buckets may have negative usable
size. This means that these buckets cannot (and will not) be used.
For larger buckets, the memory footprint may be one page greater
-than a power of 2. If so, case the corresponding power of two is
+than a power of 2. If so, the corresponding power of two is
printed in the C<APPROX> field above.
=item Free/Used
free: 8 16 32 64 128 256 512 1024 2048 4096 8192
4 12 24 48 80
-With non-C<DEBUGGING> perl, the buckets starting from C<128> have
+With a non-C<DEBUGGING> perl, the buckets starting from C<128> have
a 4-byte overhead, and thus an 8192-long bucket may take up to
8188-byte allocations.
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