=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>] ]>
8 t Trace execution
16 o Method and overloading resolution
32 c String/numeric conversions
- 64 P Print preprocessor command for -P
+ 64 P Print preprocessor command for -P, source file input state
128 m Memory allocation
256 f Format processing
512 r Regular expression parsing and execution
16384 X Scratchpad allocation
32768 D Cleaning up
65536 S Thread synchronization
+ 131072 T Tokenising
+ 262144 R Include reference counts of dumped variables (eg when using -Ds)
All these flags require B<-DDEBUGGING> when you compile the Perl
executable. See the F<INSTALL> file in the Perl source distribution
with the next one (if it exists).
For a discussion of issues surrounding file permissions and B<-i>,
-see L<perlfaq5/Why does Perl let me delete read-only files? Why
-does -i clobber protected files? Isn't this a bug in Perl?>.
+see L<perlfaq5/Why does Perl let me delete read-only files? Why does -i clobber protected files? Isn't this a bug in Perl?>.
You cannot use B<-i> to create directories or to strip extensions from
files.
=item B<-P>
-causes your program to be run through the C preprocessor before
-compilation by Perl. (Because both comments and B<cpp> directives begin
+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 "if", "else", or "define".)
+recognized by the C preprocessor such as C<"if">, C<"else">, or C<"define">.
+
+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//;
+
+because after -P this will became illegal code
+
+ s/foo
+
+The workaround is to use some other quoting separator than C<"/">,
+like for example C<"!">:
+
+ 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>
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. Since these are warnings, the B<-w> switch (or C<use
+warnings>) must be used along with this option. B<NOTE: this is
+not a substitute for -T.> This is meant only to be used as a temporary
+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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