+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