while ( <DATA> ) {
    my ( $key, $val ) = /^(\d+)\s+(\w+)/;
    $val = lc($val);
    $dict{ $val } = $key;
    }

##</code><code>##

my %dict;
while ( <DATA> ) {
    my ( $key, $val ) = /^(\d+)\s+(\w+)/;
    print "$key\t$val\n";
    $val = lc($val);
    $dict{ $val } = $key;
}
__END__
1       cross
2       reference
3       cross