Config::General::Interpolated - Parse variables within Config files


 use Config::General;
 $conf = Config::General->new(
    -ConfigFile      => 'configfile',
    -InterPolateVars => 1


This is an internal module which makes it possible to interpolate Perl style variables in your config file (i.e. $variable or ${variable}).

Normally you don't call it directly.


Variables can be defined everywhere in the config and can be used afterwards as the value of an option. Variables cannot be used as keys or as part of keys.

If you define a variable inside a block or a named block then it is only visible within this block or within blocks which are defined inside this block. Well - let's take a look to an example:

 # sample config which uses variables
 basedir   = /opt/ora
 user      = t_space
 sys       = unix
 <table intern>
     instance  = INTERN
     owner     = $user                 # "t_space"
     logdir    = $basedir/log          # "/opt/ora/log"
     sys       = macos
         misc1   = ${sys}_${instance}  # macos_INTERN
         misc2   = $user               # "t_space"

This will result in the following structure:

     'basedir' => '/opt/ora',
     'user'    => 't_space'
     'sys'     => 'unix',
     'table'   => {
          'intern' => {
                'sys'      => 'macos',
                'logdir'   => '/opt/ora/log',
                'instance' => 'INTERN',
                'owner' => 't_space',
                'procs' => {
                     'misc1' => 'macos_INTERN',
                     'misc2' => 't_space'

As you can see, the variable sys has been defined twice. Inside the <procs> block a variable ${sys} has been used, which then were interpolated into the value of sys defined inside the <table> block, not the sys variable one level above. If sys were not defined inside the <table> block then the "global" variable sys would have been used instead with the value of "unix".

Variables inside double quotes will be interpolated, but variables inside single quotes will not interpolated. This is the same behavior as you know of Perl itself.

In addition you can surround variable names with curly braces to avoid misinterpretation by the parser.


Variable names must:

  • start with a US-ASCII letter(a-z or A-Z) or a digit (0-9).

  • contain only US-ASCII letter(a-z or A-Z), digits (0-9), the dash (-) colon (:), dot (.), underscore (_) and plus (+) characters.

For added clarity variable names can be surrounded by curly braces.




 Thomas Linden <tlinden |AT|>
 Autrijus Tang <>
 Wei-Hon Chen <>


Copyright 2001 by Wei-Hon Chen <>. Copyright 2002-2022 by Thomas Linden <tlinden |AT|>.

This program is free software; you can redistribute it and/or modify it under the terms of the Artistic License 2.0.