Here is the documentation, how would you change it?

The change is fairly simple.

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). Note that 0 is a valid match offset. "undef" indicates that the search position is reset (usually due to match failure, but can also be because no match has yet been run on the scalar). "pos" directly accesses the location used by the regexp engine to store the offset, so assigning to "pos" will change that offset, and so will influence the "\G" zero-width assertion next time when this string is matched against some regular expression. Note, it does not have any influence on the currently running match. Because a failed "m//gc" match doesn't reset the offset, the return from "pos" won't change either in this case. See perlre and perlop.