See also the 2008 thread Finding match offsets of named captures in 5.10 regex, in which it is suggested that a code block can be used to capture the offset with a call to pos.

Update: An example:

 2:56 >perl -Mstrict -wE "my $s = q[My 25 cents.]; my ($p, $q); $s =~ 
+/(?<myref>(?{$p = pos})\d+(?{$q = pos}))/; say $+{myref}; say $p, q[ 
+--> ], $q;"
25
3 --> 5

 2:56 >
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