c:\@Work\Perl\monks>perl -wMstrict -le
"my $vowel = qr{ [AEIOUaeiou] }xms;
 ;;
 my $s = 'xyzzyBARxkcdFOOyz';
 ;;
 print 'offset of first vowel: ', $s =~ m{ (?= $vowel) }xms ? $+[0] : 'none';
 print 'offset of last vowel: ', $s =~ m{ .* (?= $vowel) }xms ? $+[0] : 'none';
 print 'offset of first vowel: ', 'XYZ' =~ m{ (?= $vowel) }xms ? $+[0] : 'none';
"
offset of first vowel: 6
offset of last vowel: 14
offset of first vowel: none