As per your code, your m// expression will match first digits ( 55 ) at all time as per my understanding

No, because I used m/../g in scalar context, which remembers the previous match position in pos, and then always returns the next match during subsequent calls.

Maybe you are more familiar with it in this idiom:

use 5.010;

$_ = 'a123b45c6';
while (m/(\d+)/g) {
     say $1;
}
[download]