sub is_subpenny {
    my $number = abs ($_[0] * 100);

    return $number - int ($number) > 0;
}
[download]

is faster by avoiding an extra multiply and also works for negative numbers although the abs may slow it down again.

Whether it's faster or not you'll have to determine yourself, but it's another way:

use POSIX qw[ fmod ];;
print fmod( $_, 100 ) for 12300, 12301, 12399;;
0
1
99
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how about .00001 ?

I'm not sure if I understand the question, but:

[0] Perl> print fmod( $_, 100 ) for 12300, 12301, 12399, .00001;;
0
1
99
1e-005
[download]

Or do you mean this:

[0] Perl> print fmod( $_, 1 ) for map{ ($_, -$_ ) } 12300, 12301, 1239
+9, .00001;;
0
0
0
0
0
0
1e-005
-1e-005
[download]

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw(cmpthese);

my @a = map { (rand() * 1000) / 1000 } 1 .. 1000;

cmpthese(-1, { 
  'GF'  => sub {GF($_)  for @a}, 
  'GF2' => sub {GF2($_) for @a}, 
  'dex' => sub {dex($_) for @a}, 
  'ccn' => sub {ccn($_) for @a}});


sub GF {
    my $number = abs($_[0] * 100);
    return $number - int ($number) > 0;
}


sub GF2 {
    my $number = $_[0] * 100;
    return $number - int ($number) > 0;
}

sub ccn {
    $_[0] =~ /\..../;
}

sub dex {
    my $number = $_[0];
    return (($number*100) - int($number*100) > 0);
}

__END__


      Rate  dex   GF  GF2  ccn
dex  931/s   --  -7% -19% -28%
GF  1000/s   7%   -- -13% -23%
GF2 1152/s  24%  15%   -- -11%
ccn 1297/s  39%  30%  13%   --
[download]

You took off the addition and the parens.. I got..

      Rate  ccn  dex   GF  GF2
ccn  296/s   -- -73% -74% -76%
dex 1097/s 270%   --  -2% -10%
GF  1124/s 279%   2%   --  -7%
GF2 1213/s 309%  11%   8%   --
[download]

I took off addition wittingly. One can skip addition if input data is numeric. Situation becomes worse if input must be validated.

And once again, I am not shure if we can rely on the third digit after a floating point. Indeed, I will never use that sub.

sub is_subpenny {
    ($_[0]+0) =~ /\..../;
}
[download]