Webmaster Forum / Perl / Getting Started / July 2008

I assume that Rob is talking about the $! variable:

$ perl -le' $! = $_ and print "number:", $! + 0, "  string:", $! . ""
for 5 .. 9 '
number:5  string:Input/output error
number:6  string:No such device or address
number:7  string:Argument list too long
number:8  string:Exec format error
number:9  string:Bad file descriptor

John

Perl will convert a scalar value between integer, floating point and string
representations internally depending on what your program does with the value,
and more than one representation can be valid at the same time, for instance if
I write

 my $val = '0099';
 print $val+1;

then $val will have both a string value of '0099' and an integer value of 99.

The Scalar::Util module has a function dualvar() that lets you assign both the
string and numeric value of a scalar simultaneously. Try the program below.

HTH,

Rob

use strict;
use warnings;

use Scalar::Util qw/dualvar/;
use Devel::Peek;

my $twovals = dualvar 42, 'string';

print $twovals, "\n";
print $twovals+0, "\n";