整数と小数にマッチ

 /^\d+(?:\.\d+)?$/

 #!/usr/bin/perl
 
 use strict;
 use warnings;
 
 my @nums= (
     '1.5', '0.5', '100', '0',
     '', '.1', '1.', '1.1.1', '1..1'
 );
 
 foreach my $num (@nums) {
     if ($num =~ /^\d+(?:\.\d+)?$/) {
         print "ok $num\n";
     } else {
         print "ng $num\n";
     }
 }

 ok 1.5
 ok 0.5
 ok 100
 ok 0
 ng
 ng .1
 ng 1.
 ng 1.1.1
 ng 1..1