why non-greedy modifier for one atom changes greediness of other atoms?

Example:
# select x, substring( x from E'^((.*?)(\\.[0-9]+))') from ( values ('ab.123xxx.46hfd'),('a.b.c.d.123xx')) as q (x);
        x        | substring
-----------------+-----------
 ab.123xxx.46hfd | ab.1
 a.b.c.d.123xx   | a.b.c.d.1
(2 rows)


I found in docs, that this is what happens, but I don't understand the
logic behind forcing unique greediness in whole expression.

Also - how can one write a regexp that will match "ab.123" and
"a.b.c.d.123" respectively?

in pl/perl it's of course trivial, but I can't seem to find a way to do it in substring() regexps.

Best regards,

depesz

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