NAME
    PerlX::Perform - syntactic sugar for if (defined ...) { ... }

SYNOPSIS
     my $foo = function_that_might_return_undef();
     perform { say $_ } wherever $foo;
 
     my $bar = function_that_might_return_undef();
     wherever $bar, perform { say $_ };

DESCRIPTION
    Executes some code if a given scalar is defined. Within the code block,
    the scalar is available as $_.

    Note that there is no comma before "wherever" here:

     my $foo = function_that_might_return_undef();
     perform { say $_ } wherever $foo;

    But there is one before "perform" here:

     my $bar = function_that_might_return_undef();
     wherever $bar, perform { say $_ };

  Gory Details
    The implementation is pure Perl. The closest it gets to trickery is that
    the two functions defined by this package use prototypes.

   perform
    "perform" is a function can be called in two ways:

    *   with a single coderef argument

        In this case, "perform" returns a blessed version of that coderef; a
        so-called Manifesto object.

    *   with a coderef argument followed by a scalar

        Generates the Manifesto object, and executes the Manifesto on the
        scalar, returning the result.

        Or rather, it has the effective result of doing the above. But it
        inlines the logic from PerlX::Perform::Manifesto.

   wherever
    "wherever" is a function can be called in three ways:

    *   with a single scalar argument

        In this case, "wherever" passes through the argument unchanged.

    *   with a scalar argument and a Manifesto

        In this case, "wherever" executes the Manifesto with the scalar
        argument.

    *   with a scalar argument and a coderef

        In this case, "wherever" turns the coderef into a Manifesto and
        executes it with the scalar argument.

    This means that it's possible to do this:

     my $manifesto = perform { say $_ };
     wherever $foo, $manifesto;
     wherever $bar, $manifesto;

    And indeed "wherever" does allow a little additional syntactic sugar by
    skipping over the string "perform" if it is used as the second
    parameter. Thus you can write:

     my $manifesto = perform { say $_ };
     wherever $foo, perform => $manifesto;
     wherever $bar, perform => $manifesto;

    But because PerlX::Perform::Manifesto passes through any already-blessed
    coderefs, this will work too:

     my $manifesto = perform { say $_ };
     wherever $foo, &perform($manifesto);
     wherever $bar, &perform($manifesto);

  Tail Calls
    Both "perform" and "wherever" make extensive use of "goto" in order to
    conceal their usage on the call stack.

  whenever
    This is available as an alias for "wherever", but is not exported by
    default. You need to request it like:

     use PerlX::Perform qw/perform whenever/;

BUGS
    Please report any bugs to
    <http://rt.cpan.org/Dist/Display.html?Queue=PerlX-Perform>.

SEE ALSO
    <http://www.modernperlbooks.com/mt/2012/02/a-practical-use-for-macros-in
    -perl.html>.

    Scalar::Andand.

AUTHOR
    Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE
    This software is copyright (c) 2012 by Toby Inkster.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES
    THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
    WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
    MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

