NAME

       String::Interpolate::Named - Interpolated named arguments in string

SYNOPSIS

           use String::Interpolate::Named;

           my $ctl = { args => { fn => "Johan", ln => "Bach" } };
           say interpolate( $ctl, "The famous %{fn} %{ln}." );

           # If you like object orientation.
           my $int = String::Interpolate::Named->new( { args => { ... } } );
           say $int->interpolate("The famous %{fn} %{ln}.");

DESCRIPTION

       String::Interpolate::Named provides a function to interpolate named arguments by target
       texts in a template string. The target texts are provided to the function via a hash,
       where the keys correspond to the named argument to be replaced, or a subroutine that
       performs the lookup.

   Named Arguments
       The arguments to be replaced are marked in the template by enclosing them between "%{" and
       "}". For example, the string "The famous %{fn} %{ln}." contains two named arguments, "fn"
       and "ln".

       Note that the activator may be changed from "%" into something else, see below. Throughout
       this document we use the default value.

   Basic Interpolation
       When interpolated, the keys "fn" and "ln" are looked up in the hash, and the corresponding
       values are substituted. If no value was found for a named argument, nothing is substituted
       and the "%{...}" is removed.

       You can precede "%", "{", "}" (and "|", see below) with a backslash "\" to hide their
       special meanings. For example, "\}" will not be considered closing an argument but yield a
       plain "}" in the text.

   Conditional Interpolation
       It is possible to select replacement values depending on whether the named argument has a
       value or not:

           "This book has %{title|title %{title}}"
           "This book has %{title|title %{title}|no title}"

       These are considered "%{if|then}" and "%{if|then|else}" cases.

       Assuming argument "title" has the value "My Book", in the first example the text "title My
       Book", the 'then' text, will be substituted, resulting in

           "This book has title My Title"

       If "title" does not have a value, the empty string is substituted. In the second example,
       the string "no title", the 'else' text, will be substituted.

       As can be seen, the replacement texts may contain interpolations as well. For convenience,
       you can use "%{}" to refer to the value of the named argument currently being examinated.
       The last example above can be written more shortly and elegantly as:

           "This book has %{title|title %{}|no title}"

   Testing Values
       Instead of testing for named variables to have a value, you can also test for specific
       values:

           "This takes %{days=1|%{} day|%{} days}"

   List Values
       The replacement values hash may be scalar (in general: strings and numbers) or lists of
       scalars. If a value is a list of scalars, it is possible to select a particular value from
       the list by appending an index (period and a number) to the named argument.

       Assume "customer" has value "[ "Jones", "Smith" ]", then:

           "%{customer.1} will be Smith"
           "%{customer.2} will be Jones"
           "%{customer} will be Jones Smith"

       When the value exceeds the number of elements in the list, an empty value is returned.
       When no element is selected the values are concatenated.

   The Control Hash
       The interpolation process requires two parameters: a hash with settings and values for the
       named arguments, and the string to be used as a template for interpolation. The hash will
       be further referred to as the control hash.

       The hash can have the following keys:

       args
           This is either a hash that contains replacement texts for the named variables, or a
           subroutine that gets called with a variable as argument and returns a replacement
           value.

           This element should be considered mandatory.

       separator
           The separator used to concatenate list values, see "List Values" above.

           It defaults to Perl variable $" that, on its turn, defaults to a single space.

       activator
           This is a single character that activates interpolation. By default this is the
           percent "%" character.

       keypattern
           The pattern to match key names. Default is "qr/\w+[-_\w.]*/".

       maxiter
           To enable nested substitutions and recursive replacement, the interpolation process is
           repeated until there are no more interpolations to be made. The maximun number of
           iterations is limited to the value of "maxiter".

           By default maxiter is 16.

       An example of a control hash:

           my %ctl =
             ( args => {
                 customer => [ "Jones", "Smith" ],
                 days     => 2,
                 title    => "My Title",
               },
               separator => ", ",
             );

   Object Oriented API
           my $ii = String::Interpolate::Named->new;
           $ii->ctl(\%ctl);
           $result = $ii->interpolate($template);

       For convenience, the control hash may be passed to the constructor:

           my $ii = String::Interpolate::Named->new(\%ctl);
           $result = $ii->interpolate($template);

   Functional API
       String::Interpolate::Named privides a single function, "interpolate", which is exported by
       default.

       The subroutine takes two arguments: a reference to a control hash and the template string.

          $result = interpolate( \%ctl, $template );

METHODS

   new
       Constructs a new String::Interpolate::Named object.

           my $ii = String::Interpolate::Named->new;

       or

           my $ii = String::Interpolate::Named->new(\%ctl);

   ctl
       Associates a control has with an existing object.

           $ii->ctl(\%ctl);

   interpolate
       This routine performs the actual interpolations. It can be used as a method:

           $ii->interpolate($template);

       and functional:

           interpolate( \%ctl, $template );

REQUIREMENTS

       Minimal Perl version 5.10.1.

AUTHOR

       Johan Vromans, "<JV at CPAN dot org>"

SUPPORT

       Development of this module takes place on GitHub:
       <https://github.com/sciurius/perl-String-Interpolate-Named>.

       You can find documentation for this module with the perldoc command.

           perldoc String::Interpolate::Named

       Please report any bugs or feature requests using the issue tracker on GitHub.

ACKNOWLEDGEMENTS

       Many of the existing template / interpolate / substitute modules.

COPYRIGHT & LICENSE

       Copyright 2018,2019 Johan Vromans, all rights reserved.

       This program is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.