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Re: eval {require module};?

by nobull (Friar)
on Apr 02, 2005 at 04:17 UTC ( [id://444350]=note: print w/replies, xml ) Need Help??


in reply to eval {require module};?

There are some situations (which I do not fully understand) where eval{} can trap an error and yet fail to set $@. However the return value will be undef.

So... 

unless( eval { require module; 1 } ) {
  my $err = $@ || 'eval failed but did not return error';
  # do something with $err
}

[download]
Update: instert missing 1.

Replies are listed 'Best First'.
Re^2: eval {require module};?
by nobull (Friar) on Mar 17, 2006 at 17:27 UTC
    Many months later I now know how eval{} can fail and yet not set $@. It happens if a DESTROY method called during the stack-unwind also does an eval. 
    use AtExit;

eval {
    my $q = AtExit->new(sub{eval{}});
    die "Oops\n";
};

print $@; # Prints nothing

    [download]
[reply]
[d/l]
      Which means you have to 
      sub DESTROY{
 local $@;
 eval{...}
}

      [download]
      if you want to use eval in DESTROY.
[reply]
[d/l]

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