You can do this using the pos function when performing matching against a string - This function returns the offset of where the last "m//g" search left off for the variable in question ($_ is used when the variable is not specified).

The following code demonstrates this function in action:

#!/opt/bin/perl

$str = 'The quick brown fox jumps over the lazy dog.';

while ( $str =~ /[aeiou]/ig ) {

    printf(
        "%d %s\n",
        pos( $str ), 
        substr( $str, pos( $str ) - 1 )
    );
    substr( $str, 0, pos( $str ), '' );
}
[download]