use strict;
use warnings;

my @tests = qw/12 1a 4 -3 0 0.1 .1/;

for (@tests) {
    print "$_ => ";
    no warnings qw/numeric/;
    if ($_ eq int($_) && $_ > 0) {
        print 'ok';
    } else {
        print 'bad';
    }
    print "\n";
}


__END__
C:\Perl\test>perl int_test.pl
12 => ok
1a => bad
4 => ok
-3 => bad
0 => bad
0.1 => bad
.1 => bad