Re^2: Replacing characters in a line

Why not just s/(?<=TYR )D/X/;?

Update:
Or, to keep it fixed-length:

s/^(.{21})D/$1X/;
[download]

Sidenote:
Has anyone an idea, why this:

s/^(?<=.{21})D/X/;
[download]

does not work, while this

s/(?<=.{21})D/X/;
[download]

does (but don´t use this, it´s unsafe)?

holli, /regexed monk/

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Re^3: Replacing characters in a line by manav (Scribe) on Mar 04, 2005 at 13:19 UTC
Are we sure that D will always be preceeded by "TYR " ?? Manav	[reply]
Re^4: Replacing characters in a line by holli (Abbot) on Mar 04, 2005 at 13:32 UTC
We can only tell from the example data. pelagic's regex is also unsafe. what if the line looks like `ATOM 3316 N TYR B 24 97.479 18.805 2.990 1.00 36.32 + D N` [download] Then the alone "D" at the end will be replaced by "X". Intended?? I would use the substr()-solution above. My regex was just meant as an optimization of perlsen's one, which is unneccesary complicated. Update: Striked the sillyness about the second "D". /me writes "Must read the question properly" 200 times. holli, /regexed monk/	[reply] [d/l]
Re^4: Replacing characters in a line by pelagic (Priest) on Mar 04, 2005 at 13:23 UTC
We are not! As the OP stated: there are two D's on every line. pelagic	[reply]