Question

Why does Perl warn in this case

Use of uninitialized value `$new` in substitution (s///) at ./perl.pl line 8.

and not

Use of uninitialized value `$string` in substitution (s///) at ./perl.pl line 8.

#!/usr/bin/env perl
use warnings;
use strict;

my $string;
my $new;

( $new = $string ) =~ s/^.//;

Answer 1

$string is not involved in the substitution. It’s on the RHS of an assignment, and having an undefined value on the RHS of an assignment shouldn’t trigger a warning.

If it’s ok for $new to be undefined, you could use

my $new = $string;
$new =~ s/^.// if defined($new);