=head1 SYNOPSIS
-B<perl> S<[ B<-CsTuUWX> ]>
+B<perl> S<[ B<-CsTtuUWX> ]>
S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>
S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>
sets debugging flags. To watch how it executes your program, use
B<-Dtls>. (This works only if debugging is compiled into your
Perl.) Another nice value is B<-Dx>, which lists your compiled
-syntax tree. And B<-Dr> displays compiled regular expressions. As an
-alternative, specify a number instead of list of letters (e.g., B<-D14> is
-equivalent to B<-Dtls>):
+syntax tree. And B<-Dr> displays compiled regular expressions;
+the format of the output is explained in L<perldebguts>.
+
+As an alternative, specify a number instead of list of letters (e.g.,
+B<-D14> is equivalent to B<-Dtls>):
1 p Tokenizing and parsing
2 s Stack snapshots
as it executes, the way that C<sh -x> provides for shell scripts,
you can't use Perl's B<-D> switch. Instead do this
+ # If you have "env" utility
+ env=PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program
+
# Bourne shell syntax
$ PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program
=item B<-P>
-causes your program to be run through the C preprocessor before
+B<NOTE: Use of -P is strongly discouraged because of its inherent
+problems, including poor portability.>
+
+This option causes your program to be run through the C preprocessor before
compilation by Perl. Because both comments and B<cpp> directives begin
with the # character, you should avoid starting comments with any words
recognized by the C preprocessor such as C<"if">, C<"else">, or C<"define">.
-Also, in some platforms the C preprocessor knows too much: it knows
-about the C++ -style until-end-of-line comments starting with C<"//">.
+
+If you're considering using C<-P>, you might also want to look at the
+Filter::cpp module from CPAN.
+
+The problems of -P include, but are not limited to:
+
+=over 10
+
+=item *
+
+The C<#!> line is stripped, so any switches there don't apply.
+
+=item *
+
+A C<-P> on a C<#!> line doesn't work.
+
+=item *
+
+B<All> lines that begin with (whitespace and) a C<#> but
+do not look like cpp commands, are stripped, including anything
+inside Perl strings, regular expressions, and here-docs .
+
+=item *
+
+In some platforms the C preprocessor knows too much: it knows about
+the C++ -style until-end-of-line comments starting with C<"//">.
This will cause problems with common Perl constructs like
s/foo//;
s!foo!!;
+
+
+=item *
+
+It requires not only a working C preprocessor but also a working
+F<sed>. If not on UNIX, you are probably out of luck on this.
+
+=item *
+
+Script line numbers are not preserved.
+
+=item *
+
+The C<-x> does not work with C<-P>.
+
+=back
+
=item B<-s>
enables rudimentary switch parsing for switches on the command
before being searched for on the PATH. On Unix platforms, the
program will be searched for strictly on the PATH.
+=item B<-t>
+
+Like B<-T>, but taint checks will issue warnings rather than fatal
+errors. These warnings can be controlled normally with C<no warnings
+qw(taint)>.
+
+B<NOTE: this is not a substitute for -T.> This is meant only to be
+used as a temporary development aid while securing legacy code:
+for real production code and for new secure code written from scratch
+always use the real B<-T>.
+
=item B<-T>
forces "taint" checks to be turned on so you can test them. Ordinarily
=item PERL5OPT
Command-line options (switches). Switches in this variable are taken
-as if they were on every Perl command line. Only the B<-[DIMUdmw]>
+as if they were on every Perl command line. Only the B<-[DIMUdmtw]>
switches are allowed. When running taint checks (because the program
was running setuid or setgid, or the B<-T> switch was used), this
variable is ignored. If PERL5OPT begins with B<-T>, tainting will be
Relevant only if your perl executable was built with B<-DDEBUGGING>,
this controls the behavior of global destruction of objects and other
-references.
+references. See L<perlhack/PERL_DESTRUCT_LEVEL> for more information.
+
+=item PERL_ENCODING
+
+If using the C<encoding> pragma without an explicit encoding name, the
+PERL_ENCODING environment variable is consulted for an encoding name.
=item PERL_ROOT (specific to the VMS port)
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