my @words = qw[ new old number start simple cross heavy die exit ];
my $string = q~whatever the NEw old you're trying to match~;
my $lcstring = lc $string;
my $ret = 0;
if( do {
        for my $val( @words ){
            my $r = index $lcstring, $val;
            if( $r > -1 ){
                $ret = substr $string, $r, length $val;
                last;
            }
        }
        $ret;
    } ){
    warn "the \$1 (aka ret) is => $ret\n\n";
}
__END__
the $1 (aka ret) is => NEw