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]