B::Xref(3) Perl Programmers Reference Guide B::Xref(3)NAMEB::Xref - Generates cross reference reports for Perl programs
perl -MO=Xref[,OPTIONS] foo.pl
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 File section reports on a single file. Each Subroutine section
reports on a single subroutine apart from the special cases "(defini‐
tions)" and "(main)". These report, respectively, on subroutine defini‐
tions 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 Package of each variable, subroutine
or format with the special case "(lexicals)" meaning lexical variables.
Each object name (implicitly qualified by its containing Package)
includes its type character(s) at the beginning where possible. Lexical
variables are easier to track and even included dereferencing informa‐
tion 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. Sim‐
ple uses aren't 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
Option words are separated by commas (not whitespace) and follow the
usual conventions of compiler backend options.
Directs output to "FILENAME" instead of standard output.
"-r" Raw output. Instead of producing a human-readable report, out‐
puts a line in machine-readable form for each definition/use of
"-d" Don't output the "(definitions)" sections.
(Internal) debug options, probably only useful if "-r"
included. The "t" option prints the object on the top of the
stack as it's being tracked. The "O" option prints each opera‐
tor as it's being processed in the execution order of the pro‐
Non-lexical variables are quite difficult to track through a program.
Sometimes the type of a non-lexical variable's use is impossible to
determine. Introductions of non-lexical non-scalars don't seem to be
Malcolm Beattie, email@example.com.
perl v5.8.8 2008-09-19 B::Xref(3)