#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

sub date_list {
    my @mults =qw( 2010-01-01 2010-01-02 2010-01-03 );
    return map { ($_) x 10 } @mults;                 # <--- HERE
}
say for date_list('2014-01-01', '2014-01-10');