为什么 Perl 在这种情况下会发出警告
Use of uninitialized value `$new` in substitution (s///) at ./perl.pl line 8.
并不是
Use of uninitialized value `$string` in substitution (s///) at ./perl.pl line 8.
#!/usr/bin/env perl
use warnings;
use strict;
my $string;
my $new;
( $new = $string ) =~ s/^.//;