Its better not to do detection, but simply force numification if you're expecting a number, and let warnings issue a warning

#!/usr/bin/perl --
use strict;
use warnings;
use B();
sub SvTYPE (\[$@%&*]) { use B(); ref(B::svref_2object($_[0])) }
{
    my $x = 42; 
    TYPE(\$x);
}
{
    my $x = 42.24;
    TYPE(\$x);
}
{
    my $x = "42.24"; 
    TYPE(\$x);
    $x=$x+0;
    print SvTYPE($x), "\n";
}
{
    my $x = "00042"; 
    TYPE(\$x);
    $x=$x+0;
    print SvTYPE($x), "\n";
}
{
    my $x = "42\x{260E}";
    TYPE(\$x);
}

sub TYPE { 
    no warnings;
    print $_[0],' = ', ${$_[0]},' = ', ref(B::svref_2object($_[0])), "
+\n";
}
__END__
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SCALAR(0xae664c) = 42 = B::IV
SCALAR(0xae637c) = 42.24 = B::NV
SCALAR(0xae633c) = 42.24 = B::PV
B::PVNV
SCALAR(0xae627c) = 00042 = B::PV
B::PVIV
SCALAR(0xae609c) = 42☎ = B::PV