Re^2: Perl try { } catch(e) { }

[Superfox il Volpone]

Aaaaahh I think I understood now how this is supposed to work:

#!/usr/bin/env perl


sub try(&$) {
  my ($try, $catch) = @_;
  
  eval { # perl try
    &$try
  }; if($@){ # perl catch
    &$catch($@);
  }
}
sub catch(&){ shift }

try{
  die("Frankie");
} catch {
  my $e = shift;
  print("Hello world $e\n");
}

catch { ... } is invoked before the block in the try { ...}, and all it does is to return the block as a reference to the anonymous function defined by the catch block.
Tricky mechanism.

Thanks,
s.fox

[Anonymous Monk]

If you're going to use that code instead of Try::Tiny (which by the way is pure Perl and has no non-core dependencies), make sure you read the "Background" section of Try::Tiny's docs, as there are a number of issues with $@!

[karlgoethebier]

"Aaaaahh I think I understood ..."

I don't (for the moment) - but i don't care about and just do:

#!/usr/bin/env perl

use strict;
use warnings;
use Try::Tiny;

try {
    die qq(Goodbye World!);
}
catch {
    warn $_;
};

__END__

Best regards, Karl

[jdeguest]

There is a full implementation of try-catch block using perl filters: Nice::Try So you can do something like embedded try-catch block, return, variable assignments, catching class exception, etc. There is no need for semicolon on the lack brace.

use Nice::Try;
try
{
    # do something
    die( "Argh...\n" );
}
catch( $wow )
{
    return( $self->error( "Caught an error: $wow" ) );
}
finally
{
    # do some cleanup
}

Full disclosure: I am the author of this module that I created when Devel::Declare on which TryCatch was relying became obsolete.

[haukex]

There is a full implementation of try-catch block using perl filters

Source filters are unfortunately quite dangerous, they are very prone to making code extremely brittle (Update: for example, Switch was removed from the Perl core for that reason, see e.g. Perl Code Changes Behavior if Two Subroutine definitions are swapped). Note that there is currently development underway to add try/catch to Perl natively - see Adding a try/catch syntax to Perl and Progress on try/catch.

[karlgoethebier]

See also