The B::Xref module is used to generate a cross reference listing of all
definitions and uses of variables, subroutines and formats in a Perl program.
It is implemented as a backend for the Perl compiler.
The report generated is in the following format:
object1 line numbers
object2 line numbers
Each <B>FileB> section reports on a single file. Each <B>SubroutineB> section
reports on a single subroutine apart from the special cases
(definitions) and (main). These report, respectively, on subroutine
definitions found by the initial symbol table walk and on the main part of
the program or module external to all subroutines.
The report is then grouped by the <B>PackageB> of each variable,
subroutine or format with the special case (lexicals) meaning
lexical variables. Each <B>objectB> name (implicitly qualified by its
containing <B>PackageB>) includes its type character(s) at the beginning
where possible. Lexical variables are easier to track and even
included dereferencing information where possible.
The line numbers are a comma separated list of line numbers (some
preceded by code letters) where that object is used in some way.
Simple uses arent preceded by a code letter. Introductions (such as
where a lexical is first defined with my) are indicated with the
letter i. Subroutine and method calls are indicated by the character
&. Subroutine definitions are indicated by s and format
definitions by f.
For instance, heres part of the report from the pod2man program that
comes with Perl:
$ready_to_print i1069, 1079
$2 1085, 1085
$3 1085, 1085
%HTML_Escapes 1085, 1085
This shows the variables used in the subroutine clear_noremap. The
variable $ready_to_print is a my() (lexical) variable,
<B>iB>ntroduced (first declared with my()) on line 1069, and used on
line 1079. The variable $& from the main package is used on 1086,
and so on.
A line number may be prefixed by a single letter:
The most useful option the cross referencer has is to save the report
to a separate file. For instance, to save the report on
myperlprogram to the file report:
Lexical variable introduced (declared with my()) for the first time.
Subroutine or method call.
$ perl -MO=Xref,-oreport myperlprogram