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'Native' try {} catch {} semantics for perl using Devel::Declare
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    TryCatch - first class try catch semantics for Perl, without source

     use TryCatch;

     sub foo {
       my ($self) = @_;

       try {
         die Some::Class->new(code => 404 ) if $self->not_found;
         return "return value from foo";
       catch (Some::Class $e where { $_->code > 100 } ) {

    This module aims to give first class exception handling to perl via
    'try' and 'catch' keywords. The basic syntax this module provides is
    "try { # block }" followed by zero or more catch blocks. Each catch
    block has an optional type constraint on it the resembles Perl6's method

    Also worth noting is that the error variable ($@) is localised to the
    try/catch blocks and will not leak outside the scope, or stomp on a
    previous value of $@.

    The simplest case of a catch block is just

     catch { ... }

    where upon the error is available in the standard $@ variable and no
    type checking is performed. The exception can instead be accessed via a
    named lexical variable by providing a simple signature to the catch
    block as follows:

     catch ($err) { ... }

    Type checking of the exception can be performed by specifing a type
    constraint or where clauses in the signature as follows:

     catch (TypeFoo $e) { ... }
     catch (Dict[code => Int, message => Str] $err) { ... }

    As shown in the above example, complex Moose types can be used,
    including MooseX::Types style of type constraints

    In addition to type checking via Moose type constraints, you can also
    use where clauses to only match a certain sub-condition on an error. For
    example, assuming that "HTTPError" is a suitably defined TC:

     catch (HTTPError $e where { $_->code >= 400 && $_->code <= 499 } ) { 
       return "4XX error";
     catch (HTTPError $e) {
       return "other http code";

    would return "4XX error" in the case of a 404 error, and "other http
    code" in the case of a 302.

    In the case where multiple catch blocks are present, the first one that
    matches the type constraints (if any) will executed.

    return. You can put a return in a try block, and it would do the right
    thing - namely return a value from the subroutine you are in, instead of
    just from the eval block.

    Type Checking. This is nothing you couldn't do manually yourself, it
    does it for you using Moose type constraints.

    *   Decide on "finally" semantics w.r.t return values.

    *   Write some more documentation

    MooseX::Types, Moose::Util::TypeConstraints, Parse::Method::Signatures.

    Ash Berlin <>

    Thanks to Matt S Trout and Florian Ragwitz for work on Devel::Declare
    and various B::Hooks modules

    Vincent Pit for Scope::Upper that makes the return from block possible.

    Licensed under the same terms as Perl itself.

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