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How do I substitute case insensitively on the LHS, but preserving case on the RHS?

by faq_monk (Initiate)
on Oct 08, 1999 at 00:25 UTC ( #660=perlfaq nodetype: print w/replies, xml ) Need Help??

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

It depends on what you mean by ``preserving case''. The following script makes the substitution have the same case, letter by letter, as the original. If the substitution has more characters than the string being substituted, the case of the last character is used for the rest of the substitution.

    # Original by Nathan Torkington, massaged by Jeffrey Friedl
    #
    sub preserve_case($$)
    {
        my ($old, $new) = @_;
        my ($state) = 0; # 0 = no change; 1 = lc; 2 = uc
        my ($i, $oldlen, $newlen, $c) = (0, length($old), length($new));
        my ($len) = $oldlen < $newlen ? $oldlen : $newlen;

        for ($i = 0; $i < $len; $i++) {
            if ($c = substr($old, $i, 1), $c =~ /[\W\d_]/) {
                $state = 0;
            } elsif (lc $c eq $c) {
                substr($new, $i, 1) = lc(substr($new, $i, 1));
                $state = 1;
            } else {
                substr($new, $i, 1) = uc(substr($new, $i, 1));
                $state = 2;
            }
        }
        # finish up with any remaining new (for when new is longer than old)
        if ($newlen > $oldlen) {
            if ($state == 1) {
                substr($new, $oldlen) = lc(substr($new, $oldlen));
            } elsif ($state == 2) {
                substr($new, $oldlen) = uc(substr($new, $oldlen));
            }
        }
        return $new;
    }

    $a = "this is a TEsT case";
    $a =~ s/(test)/preserve_case($1, "success")/gie;
    print "$a\n";

This prints:

    this is a SUcCESS case

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1nickt gives up on finding a Perl YAML parser that supports hash merging. In 2017.
[LanX]: Oh yes true, he lost his accent! xD
[Eily]: and since his name is a modified version of astérisque (asterisk), which is a typographical symbol, I think it's even funnier that he would lose a diacritic
[Eily]: the pun doesn't work so well with "he lost a diacritic" though :P
[LanX]: Obelix might offer to find it again ...
[LanX]: not much to translate anyway since Goscinny died
[Eily]: https://en. wikipedia.org/ wiki/List_of_Aster ix_characters some of the names were changed to include a new pun
[LanX]: sure some are even funnier now
[LanX]: some lost because they were not translated like Epidemais

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