Just an idea, I'm not sure whether you can use it.

If you make a copy of a large string you've read, the two copies will have separate pos-itions, thus, you can traverse both with regexps without the need for substr'ing it.

For example: 

$string1= "hello, world\n"; $string2= $string1; pos($string1)= 4; whil
+e ($string1=~/(.)/gs) {$win_right= $1; $string2=~/(.)/gs; $win_left= 
+$1; print " "x$n++, "$win_left...$win_right\n"}

[download]

prints: 

h...o
 e...,
  l...
   l...w
    o...o
     ,...r
       ...l
       w...d
        o...

[download]

This will of course have difficulties on what to do at the boundary of two blocks you've read.

Update: spelling. Whether, whether, whether, whether, I'll have to learn this eventually.

In reply to Re: character-by-character in a huge file by ambrus
in thread character-by-character in a huge file by mushnik

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