#!/usr/bin/perl -w
$_= "193287461528";
"0 but true" while s/(\d)(\d\d\d)(\D|$)/$1,$2$3/;
print;

##</code><code>##

Useless use of a constant in void context at warn.pl line 3.
193,287,461,528

##</code><code>##

#!/usr/bin/perl -w
$_= "193287461528";
sub zero() { "0 but true" }
BEGIN {
    if(  @ARGV  ) {
        eval '0+zero';
    }
}
zero while s/(\d)(\d\d\d)(\D|$)/$1,$2$3/;
print;

##</code><code>##

$ perl warn.pl
Useless use of a constant in void context at warn.pl line 9.
193,287,461,528
$ perl warn.pl x
193,287,461,528

##</code><code>##

#!/usr/bin/perl -w
$_= "193287461528";
sub zero() { "0 but true" }
zero while s/(\d)(\d\d\d)(\D|$)/$1,$2$3/;
print;
my $x= 0+zero;