Help understanding global flag in perl

As far as I know in perl global '/g' flag means that search will replace/return all the matches throughout the string. But I am not able to understand the way it reacts to global variables while matching, can somebody explain the why there is difference between output of these two sample programs:

Version 1:

my $text = 'This is sample float value 3.2 ';

getFloat();
getFloat();

sub getFloat(){
    if ($text =~ /([0-9]+?)(.?)([0-9]+?)/is){
        print "matched> $1$2$3 ";
    }
}

Output: matched> 3.2 matched> 3.2

Version 2:(with global flag)

my $text = 'This is sample float value 3.2 ';

getFloat();
getFloat();

sub getFloat(){
    if ($text =~ /([0-9]+?)(.?)([0-9]+?)/gis){
        print "matched> $1$2$3 ";
    }
}

Output: matched> 3.2

As seen from outputs, with global flag matching occurs only once. Can someone explain this behaviour.