while ( ... )
{
    ...
}
continue
{
    # Reset the position of the regex match so that it will restart
    # just after the start of this match. This is done inside continue{}
    # to safeguard itself against a next() that someone else might
    # add later.
    pos() = $-[0] + 1;
}
##</code><code>##

while ( /($regex)/gx )
{
    push @substrings,
        { match => $1,
          pos   => ( pos() - length $1 ),
          length => length $1,};

    # Restart the checking at one character after the match started.
    pos() = $-[0] + 1;
}