Escaping regular expressions in plperl

How should one escape regular expressions in plperl?

In the following chunk of PlPerl code the date doesn't match  the regex:

my $endby = '2009-06-13';

my $t = spi_exec_query(qq|SELECT CASE WHEN '$endby'  ~ E'.*\\d\\d\\d\\d
\\-\\d\\d?\\-\\d\\d?.*'
         THEN '$endby'::timestamptz ELSE CURRENT_DATE::timestamptz END AS
test|);

  die "$t->{rows}[0]{test}";

However, when I run the following query using PgAdmin, the date DOES
match the regex.

SELECT CASE WHEN '$endby'  ~ E'.*\\d\\d\\d\\d\\-\\d\\d?\\-\\d\\d?.*'
         THEN '$endby'::timestamptz ELSE CURRENT_DATE::timestamptz END AS
test