You want something like:

sub in_eval {
   my $i=0;
   while (my @caller=caller($i++)) {
      return defined $caller[6] ? "eval EXPR"
                                : "eval BLOCK"
         if !$caller[7] && $caller[3] eq "(eval)"
   }
}
...
die @_ if defined $^S ? $^S : in_eval;
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See perldoc caller for explanation. (I seem to recall there may be times when $^S is inaccurate; if so, just use die @_ if in_eval.)