The sentient life form Paul posted the following:
> 3: time_line =~ s/(^\d+\/)0/\1/;
> ---
...
>
> ==> What does line 3 do??
(^\d+\/)
^ is start of line
\d+ is 1 or more digits
\/ is an escaped /, which is i.e. a /
what matches between the braces ( and ) gets put in $1, which is also
accessible as \1
so one or more digits from the start of the line and a / character are
matched and put in $1 (accessible via \1 too).
The 0 that follows in the regexp is outside the braces and not put in $1,
hence the \1 in the substitute part of the regexp only contains the digits
and /, without a 0 following, hence the is removed.
So it removes the 'second' zero in the string.