Hi Nicholas,
The perlvar manpage indicates that you may only assign
an errno to $!, making no mention of assigning to it
custom error messages.
Many modules work around this by defining a global
$Module::error or some such variable that defines the
last error message generated (.e.g, the $DBI::errstr
global). It's less cute than
foo() or die "Can't foo: $!";
, but it's much more flexible.
Others might advocate the eval BLOCK statement
combined with the $@ built-in (see the perlfunc
manpage). In that case, rather than setting $!, you'd
die() (which sets $@ to the die()'s argument). And to
prevent your script from exiting upon die()ing, you'd
wrap your function call in an eval BLOCK statement,
and test the value of $@ afterwards. For (a contrived
and untested) example:
sub divide {
my($dividend, $divisor) = @_;
die "Illegal divide by zero" if $divisor == 0;
return $dividend / $divisor;
}
eval {
my $answer = divide( 4 / 0 );
};
if($@) {
"Couldn't divide: $@";
}
Or if you want to go further, check out
Class::Exception. I haven't (directly) used it myself,
so I make no promises of its utility.
As always, there are probably more ways of handling
exceptions than you can shake a stick at. Thankfully
with Perl 6 we'll be getting something a little more
standard (whatever that means).
Cheers,
David
--- "Nicholas G. Thornton"
<[EMAIL PROTECTED]> wrote:
> (this seemed not to go through last time I sent it,
> daemon returned a failure)
>
> I'm working on expanding a module I wrote a while
> back and one of the things I'm
> adding is an input filter. I'd like to have bad
> input return an error (to $!
> perhaps/preferably) so you could write something
> like:
>
> &function() or die "Error: $!";
>
> .. but if the input is fine it returns either the
> input (as it's currently
> designed) or a true value (the easier way). Either
> way I was wondering how to
> set $! since = doesn't seem to work.
>
> ~wren
>
>
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