I'm not sure I see your point. How exactly do you define a "user-level" error?

What is the significant difference between the two subs in the following code?

sub foo {
    eval {
        my $m = shift;
        die $m;
    };
    return;
}

sub bar {
    my $m = shift;
    $@ = $m . ' at ' . __FILE__ . ' line ' . __LINE__ . "\n";
    return
}

foo("foo message");
print "foo $@";
bar("bar message");
print "bar $@";
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I don't see how it could hurt anything to set it explicitly as long as you document that your code uses it to return an error. That's not to say I'm a fan of this approach (I'm not), but I am suspicious of your claim that it would "make it much harder to program for evals."

And if you set $@ in the middle of your code, you lose the eval error!

But, if you want to rely on $@, you had better inspect it immediately after your eval() anyway. That is, unless you trust everyone else's code to always localize $@ and be free from compile time errors in their eval BLOCKs.

-sauoq
"My two cents aren't worth a dime.";