NAME
    "String::MatchInterpolate" - named regexp capture and interpolation from
    the same template.

SYNOPSIS
     use String::MatchInterpolate;

     my $smi = String::MatchInterpolate->new( 'My name is ${NAME/\w+/}' );

     my $vars = $smi->match( "My name is Bob" );
     my $name = $vars->{NAME};

     print $smi->interpolate( { NAME => "Jim" } ) . "\n";

DESCRIPTION
    This module provides an object class which represents a string matching
    and interpolation pattern. It contains named-variable placeholders which
    include a regexp pattern to match them on. An instance of this class
    represents a single pattern, which can be matched against or
    interpolated into.

    Objects in this class are not modified once constructed; they do not
    store any runtime state other than data derived arguments passed to the
    constructor.

  Template Format
    The template consists of a string with named variable placeholders
    embedded in it. It looks similar to a perl or shell string with
    interpolation:

     A string here with ${NAME/pattern/} interpolations

    The embedded variable is delmited by perl-style "${ }" braces, and
    contains a name and a pattern. The pattern is a normal perl regexp
    fragment that will be used by the "match()" method. This regexp should
    not contain any capture brackets "( )" as these will confuse the parsing
    logic.

    Outside of the embedded variables, the string is interpreted literally;
    i.e. not as a regexp pattern. A backslash "\" may be used to escape the
    following character, allowing literal backslashes or dollar signs to be
    used.

    The intended use for this object class is that the template strings
    would come from a configuration file, or some other source of "trusted"
    input. In the current implementation, there is nothing to stop a
    carefully-crafted string from containing arbitrary perl code, which
    would be executed every time the "match()" or "interpolate()" methods
    are called. (See "SECURITY" section). This fact may be changed in a
    later version.

  Suffices
    By default, the beginning and end of the string match are both anchored.
    If the "allow_suffix" option is passed to the constructor, then the end
    of the string is not anchored, and instead, any suffix found by the
    "match()" method will be returned in a hash key called "_suffix". This
    may be useful, for example, when matching directory names, URLs, or
    other cases of strings with unconstrained suffices. The "interpolate()"
    method will not recognise this hash key; instead just use normal string
    concatenation on the result.

     my $userhomematch = String::MatchInterpolate->new(
        '/home/${USER/\w+/}/',
        allow_suffix => 1
     );

     my $vars = $userhomematch->match( "/home/fred/public_html" );
     print "Need to fetch file $vars->{_suffix} from $vars->{USER}\n";

CONSTRUCTOR
  $smi = String::MatchInterpolate->new( $template, %opts )
    Constructs a new "String::MatchInterpolate" object that represents the
    given template and returns it.

    $template
            A string containing the template in the format given above

    %opts   A hash containing extra options. The following options are
            recognised:

            allow_suffix
                A boolean flag. If true, then the end of the string will not
                be anchored, and instead, an extra suffix will be allowed to
                follow the matched portion. It will be returned as "_suffix"
                by the "match()" method.

METHODS
  $vars = $smi->match( $str )
    Attempts to match the given string against the template. If successful,
    returns a HASH reference containing the values of the captures. If the
    string fails to match, "undef" is returned.

    $str    The string to match

  $str = $smi->interpolate( $vars )
    Interpolates the given variable values into the template and returns the
    generated string.

    $vars   Reference to a HASH containing the variable values to
            interpolate

  @vars = $smi->vars()
    Returns the list of variable names defined / used by the template.

BENCHMARKS
    The template is compiled into a pair of strings containing perl code,
    which implement the matching and interpolation operations using normal
    perl regexps and string contatenation. These strings are then "eval()"ed
    into CODE references which the object stores. This makes it faster than
    a simple regexp that operates over the template string each time a match
    or interpolation needs to be performed. The following output compares
    the speed of "String::MatchInterpolate" against both direct hard-coded
    perl, and simple regexp operations.

     Comparing 'interpolate':
     
            Rate   s///  S::MI native
     s///    81938/s     --   -44%   -90%
     S::MI  145232/s    77%     --   -82%
     native 806800/s   885%   456%     --
     
 Comparing 'match':
     
            Rate    m//  S::MI native
     m//     35354/s     --   -46%   -73%
     S::MI   65749/s    86%     --   -50%
     native 131885/s   273%   101%     --

    (This was produced by the benchmark.pl file in the module's
    distribution.)

SECURITY CONSIDERATIONS
    Because of the way the optimised match and interpolate functions are
    generated, it is possible to inject arbitrary perl code via the template
    given to the constructor. As such, this object should not be used when
    the source of that template is considered untrusted.

    Neither the "match()" nor "interpolate()" methods suffer this problem;
    any input into these is safe from exploit in this way.

SEE ALSO
    The following may be used to provide just "interpolate()"-style
    operations:

    *   String::Interpolate - Wrapper for builtin the Perl interpolation
        engine

    *   Text::Sprintf::Named - sprintf-like function with named conversions

    The following may be used to provide just "match()"-style operations:

    *   Regexp::NamedCaptures - Saves capture results to your own variables

    *   perlre(1) - named capture buffers in perl 5.10 (the
        "(?<NAME>pattern)" format)

AUTHOR
    Paul Evans <leonerd@leonerd.org.uk>

