What you're seeing here is an 'x' of the print's return value, which is of course 1 since the print succeeded. We can expand the replacement eval with a crude check for the function being a print, in which case we leave $onetimeDump off.

sub smarter_eval {
  local $onetimeDump = 'dump'
    if $_[0] =~ /\Aprint\s*\(?/;
  old_eval(@_);
}
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