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

my %hash = (
    foo => {
        bar => "SELECT * FROM mytable ",
    },
);
$hash{foo}{bar} .= "WHERE user=? ";
$hash{foo}{bar} .= "AND email=? ";

use Data::Dumper;
print Dumper \%hash;
__END__
$VAR1 = {
          'foo' => {
                     'bar' => 'SELECT * FROM mytable WHERE user=? AND email=? '
                   }
        };