Well you could use

print "contains fractional component\n" if $number =~ /\.(?!0*$)/;
[download]

But that'll fail for large numbers.

sub r { $_[0] ? 'fractional' : 'integer' }

for my $n (
   '1.00',
   2**50,
) {
   print(
      "$n:\n",
      "method 1: ", r( $n =~ /\./                      ), "\n",
      "method 2: ", r( $n =~ /\.(?!0*$)/               ), "\n",
      "method 3: ", r( sprintf('%f',$n) =~ /\.(?!0*$)/ ), "\n",
      "method 4: ", r( int($_)!=$_                     ), "\n",
      "\n",
   );
}
[download]

1.00:
method 1: fractional
method 2: integer
method 3: integer
method 4: integer

1.12589990684262e+015:
method 1: fractional
method 2: fractional
method 3: integer
method 4: integer
[download]