So I accessed today to the code.
It was a regular expression which tries to match (number1) with (measuring units1){optional}, and (number2 with units2){optional}.
The shortened for simplicity regex looks like that:
/^
(?: ' \s* )?
($positive_number){1}+ \s* (?: \( \s* ($stdev) \s* \) )?
\s* ($units_1)?
(
    \s* ($positive_number) \s* (?: \( \s* ($stdev) \s* \) )?
    \s* ($units_2)
)?
(?: \s* ' )?
$/x

[download]
For example: $units_1 = "A|B3"; $units_2 = "C|D-3"; Then regex should match:
20B3
20 B3 15 D-3
20A15C

[download]
but it shouldn't match 20C.
With new backtracking it matches 20C as (2, undef, undef, 0, undef, C) === ($1, $2, $3, $4, $5, $6)

In reply to Re^7: about style: use possessive or atomic? by rsFalse
in thread about style: use possessive or atomic? by rsFalse

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