Thank you very much for this!
I tried it and it works, but I think there is a problem if the string does not contain NNNNN but only --- and BBBB.
I tried this:
$initial_string = '---------------------------------------------------
+---------------------------------------------------------------------
+---------------------------------------------------------------------
+------------------------------------------------------------------BBB
+BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB-----------------';

print $initial_string."\n";
$maxLen = 200;
$initial_string =~ s/((?=N-+)(?:N)(?:-*?))(-{1,$maxLen}B)/$1 . ('B' x 
+length $2)/eg;
$initial_string =~ s/(B-{1,$maxLen})(?=-*(N|$))/'B' x length $1/eg;
print $initial_string."\n";

[download]

and it only expanded the BBBB substring to the right of it, not to the left.

In reply to Re^2: How can I expand my substring? by Anonymous Monk
in thread How can I expand my substring? by Anonymous Monk

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