perldoc -f pos yields

       pos SCALAR
       pos     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).  May be modi-
               fied to change that offset.  Such modification
               will also influence the "\G" zero-width assertion
               in regular expressions.  See perlre and perlop.
[download]

so yes, you can use  pos() to reset the position.

The error

panic: sv_pos_b2u: bad byte offset at [...].
[download]

looks like a perl bug to me, This routine converts a byte position to a unicode character position and translation should be transparent to the user.

-Mark