Interesting...

This might not be the most efficient way to do it, but you could do: 

#!/usr/bin/perl -w

use strict;

while(<>) {
         s/(.*?)(....)$/("X" x length($1)).$2/e;
         print;
}

[download]
The efficient way is probably: 
#!/usr/bin/perl -w

use strict;

while(<>) {
    chomp;
    if(length > 4) {
         my $tail = substr($_,-4);
         $_=('X'x (length($_)-4)).$tail;
    }
    print "$_\n";
}

[download]
Of course, I could be wrong; the regex could be faster than substr. I'll defer to someone with enough tuits to run a benchmark :)
--
Mike

Edit: maverick (++) had the tuits; substr wins by a large margin.

In reply to s///e by RMGir
in thread How do I replace all characters in a string with X's except the last 4 character by Anonymous Monk

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