#!perl

for $invalue (qw/ 1 -10 abc /) {

    eval{ local $^W = 1; $invalue + 0 };   ### Is Number?
    if ( $@ ) {
        print "$invalue is *not* a Number; Details: $@\n";
    } else {
        print = "$invalue appears to be a number.\n";
    }

}

##</code><code>##

1 appears to be a number.
-10 appears to be a number.
Argument "abc" isn't numeric in add at num.pl line 3.
abc appears to be a number.

##</code><code>##

#!perl

for $invalue (qw/ 1 -10 abc /) {

    eval{ local $SIG{__WARN__} = sub { die @_ };
          local $^W = 1; () = $invalue + 0 };   ### Is Number?
    if ( $@ ) {
        print "$invalue is *not* a Number; Details: $@\n";
    } else {
        print "$invalue appears to be a number.\n";
    }

}

##</code><code>##

1 appears to be a number.
-10 appears to be a number.
abc is *not* a Number; Details: Argument "abc" isn't numeric in add at num.pl line 4.