Programming Perl, 3rd Edition

Code Development Tools

The O module has many interesting Modi Operandi beyond feeding the exasperatingly experimental code generators. By providing relatively painless access to the Perl compiler's output, this module makes it easy to build other tools that need to know everything about a Perl program.

The B::Lint module is named after lint (1), the C program verifier. It inspects programs for questionable constructs that often trip up beginners but don't normally trigger warnings. Call the module directly:

% perl -MO=Lint,all myprog

Only a few checks are currently defined, such as using an array in an implicit scalar context, relying on default variables, and accessing another package's (nominally private) identifiers that start with _. See B::Lint (3) for details.

The B::Xref module generates cross-reference listings of the declaration and use of all variables (both global and lexically scoped), subroutines, and formats in a program, broken down by file and subroutine. Call the module this way:

% perl -MO=Xref myprog > myprof.pxref

For instance, here's a partial report:

Subroutine parse_argv
  Package (lexical)
    $on               i113, 114
    $opt              i113, 114
    %getopt_cfg       i107, 113
    @cfg_args         i112, 114, 116, 116
  Package Getopt::Long
    $ignorecase       101
    &GetOptions       &124
  Package main
    $Options          123, 124, 141, 150, 165, 169
    %$Options         141, 150, 165, 169
    &check_read       &167
    @ARGV             121, 157, 157, 162, 166, 166

This shows that the parse_argv subroutine had four lexical variables of its own; it also accessed global identifiers ...