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.\" ========================================================================
.\"
.IX Title "General::Interpolated 3pm"
.TH General::Interpolated 3pm "2022-10-13" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
Config::General::Interpolated \- Parse variables within Config files
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 5
\& use Config::General;
\& $conf = Config::General\->new(
\&    \-ConfigFile      => \*(Aqconfigfile\*(Aq,
\&    \-InterPolateVars => 1
\& );
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is an internal module which makes it possible to interpolate
Perl style variables in your config file (i.e. \f(CW$variable\fR
or \f(CW\*(C`${variable}\*(C'\fR).
.PP
Normally you don't call it directly.
.SH "VARIABLES"
.IX Header "VARIABLES"
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.
.PP
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:
.PP
.Vb 10
\& # 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
\&     <procs>
\&         misc1   = ${sys}_${instance}  # macos_INTERN
\&         misc2   = $user               # "t_space"
\&     </procs>
\& </table>
.Ve
.PP
This will result in the following structure:
.PP
.Vb 10
\& {
\&     \*(Aqbasedir\*(Aq => \*(Aq/opt/ora\*(Aq,
\&     \*(Aquser\*(Aq    => \*(Aqt_space\*(Aq
\&     \*(Aqsys\*(Aq     => \*(Aqunix\*(Aq,
\&     \*(Aqtable\*(Aq   => {
\&          \*(Aqintern\*(Aq => {
\&                \*(Aqsys\*(Aq      => \*(Aqmacos\*(Aq,
\&                \*(Aqlogdir\*(Aq   => \*(Aq/opt/ora/log\*(Aq,
\&                \*(Aqinstance\*(Aq => \*(AqINTERN\*(Aq,
\&                \*(Aqowner\*(Aq => \*(Aqt_space\*(Aq,
\&                \*(Aqprocs\*(Aq => {
\&                     \*(Aqmisc1\*(Aq => \*(Aqmacos_INTERN\*(Aq,
\&                     \*(Aqmisc2\*(Aq => \*(Aqt_space\*(Aq
\&            }
\&         }
\&     }
.Ve
.PP
As you can see, the variable \fBsys\fR has been defined twice. Inside
the <procs> block a variable ${sys} has been used, which then were
interpolated into the value of \fBsys\fR defined inside the <table>
block, not the sys variable one level above. If sys were not defined
inside the <table> block then the \*(L"global\*(R" variable \fBsys\fR would have
been used instead with the value of \*(L"unix\*(R".
.PP
Variables inside double quotes will be interpolated, but variables
inside single quotes will \fBnot\fR interpolated. This is the same
behavior as you know of Perl itself.
.PP
In addition you can surround variable names with curly braces to
avoid misinterpretation by the parser.
.SH "NAMING CONVENTIONS"
.IX Header "NAMING CONVENTIONS"
Variable names must:
.IP "\(bu" 4
start with a US-ASCII letter(a\-z or A\-Z) or a digit (0\-9).
.IP "\(bu" 4
contain only US-ASCII letter(a\-z or A\-Z), digits (0\-9), the dash (\-)
        colon (:), dot (.), underscore (_) and plus (+) characters.
.PP
For added clarity variable names can be surrounded by curly braces.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Config::General
.SH "AUTHORS"
.IX Header "AUTHORS"
.Vb 3
\& Thomas Linden <tlinden |AT| cpan.org>
\& Autrijus Tang <autrijus@autrijus.org>
\& Wei\-Hon Chen <plasmaball@pchome.com.tw>
.Ve
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2001 by Wei-Hon Chen <plasmaball@pchome.com.tw>.
Copyright 2002\-2022 by Thomas Linden <tlinden |AT| cpan.org>.
.PP
This program is free software; you can redistribute it and/or
modify it under the terms of the Artistic License 2.0.
.PP
See <http://www.perl.com/perl/misc/Artistic.html>
.SH "VERSION"
.IX Header "VERSION"
2.16