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 donīt use this, itīs unsafe)?


holli, /regexed monk/

In reply to Re^2: Replacing characters in a line by holli
in thread Replacing characters in a line by Becky

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