$ perl -MB -E 'my $x = 1; say B::class(B::svref_2object(\$x)) eq "IV" ? "yes" : "no" '
yes

$ perl -MB -E 'my $x = "1"; say B::class(B::svref_2object(\$x)) eq "IV" ? "yes" : "no" '
no


##</code><code>##

use strict;
use warnings;
use Benchmark qw/:all/;
use B;
use Scalar::Util qw/looks_like_number/;


cmpthese(-1, {
 iv => sub { my $r; for my $var (1...1000) { $r = B::class(B::svref_2object(\$var)) eq 'IV'  } },
 ref => sub { my $r; for my $var (1...1000) { $r = ref($var) eq ''   } },
 lln => sub { my $r; for my $var (1...1000) { $r = Scalar::Util::looks_like_number($var)   } },
});
__END__
iv    806/s    --  -93%  -95%
lln 12047/s 1394%    --  -18%
ref 14768/s 1732%   23%    --

__END__
       Rate    iv   lln   ref
iv    799/s    --  -93%  -95%
lln 11821/s 1379%    --  -20%
ref 14768/s 1748%   25%    --