I've got a list that I want to round at a variable granularity, e.g.:

sub round_all {
  my $interval = shift;
  my @result;
  foreach $value (@_) {
    my $quanta = int(($value + $interval/2) / $interval);
    push @result, $quanta * $interval;
  }
  @result;
}
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however, not all values in the list are guaranteed to be numbers. If the value is not a number, I want it left intact in the resulting list. Something like:

sub round_all {
  my $interval = shift;
  my @result;
  foreach $value (@_) {
    if(isnumber($value) {
      my $quanta = int(($value + $interval/2) / $interval);
      push @result, $quanta * $interval;
    }
    else {
      push @result, $value;
    }
  }
  @result;
}
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Is there a simple, non-ugly way to tell what is a number and what isn't?

2006-05-08 Retitled by g0n, as per Monastery guidelines
Original title: 'isnumber() ??'