Re^2: matching operator question

Sorry, I do understand regex's but I screwed up my question - I meant to have said I need a way for $foo =~ s/a/X/ to match the LAST letter a, not the first.

And now I see that I can just reverse the string first, then reverse it again after the replace.

I thought maybe there was an option for the s operation that would go in reverse order (like how the g option makes it global in s/a/X/g )

Thanks for your replies.

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Re^3: matching operator question by tlm (Prior) on May 13, 2005 at 21:41 UTC
If you're matching a simple string (e.g. 'b'), as opposed to a general regexp pattern, then I think the `rindex` solution proposed by Transient and Animator is the way to go. For more complicated matches, you could use a negative look-ahead assertion to single out the last occurrence; e.g. to replace the last occurrence of the pattern `/[AB]/` with `X`, you could use `s/[AB](?!.*[AB])/X/s` [download] This will replace the last occurrence of `A` or `B` with `X`. The `/s` modifier is necessary in case the string contains embedded newlines. the lowliest monk	[reply] [d/l]

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Re^3: matching operator question
by tlm (Prior) on May 13, 2005 at 21:41 UTC

If you're matching a simple string (e.g. 'b'), as opposed to a general regexp pattern, then I think the rindex solution proposed by Transient and Animator is the way to go. For more complicated matches, you could use a negative look-ahead assertion to single out the last occurrence; e.g. to replace the last occurrence of the pattern /[AB]/ with X, you could use

s/[AB](?!.*[AB])/X/s
[download]

A

B

X

/s

the lowliest monk

[reply]
[d/l]