Regular expression to match a string in incorrect case

Question

How do I write a regular expression that matches a particular string in all combinations of upper and lower case letters except for one?

For example, take the string "SuperMario". What regular expression matches that string in all other combinations of upper and lower case letters?

The regular expression should match:

sUPERmARIO
Supermario

The regular expression should not match:

SuperMario
Supermari

Perl compatible regular expression preferred.

possible duplicate of [What Perl regex can match CamelCase words?](http://stackoverflow.com/questions/815787/what-perl-regex-can-match-camelcase-words) — Burhan Khalid, Jun 16 '13 at 04:51
must it be regex? what you want is case-sensitive string comparison to be false AND case-insensitive comparison to be true — cbayram, Jun 16 '13 at 05:15

Casimir et Hippolyte · Accepted Answer · 2016-07-26T12:02:09.213

10

You can use this:

/(?!SuperMario)(?i)supermario/

EDIT:

Note that you will have better performances with a lookbehind, if your string contains other things:

/(?i)supermario(?<!(?-i)SuperMario)/

edited Jul 26 '16 at 12:02

answered Jun 16 '13 at 05:03

Casimir et Hippolyte

88,009
5
94
125

perreal · Answer 2 · 2013-06-16T05:10:41.293

3

my $s = "Supermario";
if ($s =~ /supermario/i and $s !~ /SuperMario/) {
    print "wrong\n";
}

Another method:

/(?:[S](?!uperMario)|s)[Uu][Pp][eE][rR][mM][aA][Rr][iI][oO]/

edited Jun 16 '13 at 05:10

answered Jun 16 '13 at 04:53

perreal

94,503
21
155
181

Sorry, I'm not actually using Perl, I'm using something that accepts Perl-compatible regular expressions. Updated the question to clarify. – Joe Daley Jun 16 '13 at 05:01
still, you can do case-insensitive match and also negate the result of proper form. – perreal Jun 16 '13 at 05:03
@JoeDaley, added an alternative – perreal Jun 16 '13 at 05:10

cbayram · Answer 3 · 2013-06-16T05:11:51.627

0

My Perl is rusty, and this is not using regex, but how about:

my $term = "SuperMario";
my $input = "SuperMario";
if ( $input ne $term && uc($input) eq uc($term) ){
    print "match";
}

edited Jun 16 '13 at 05:11

answered Jun 16 '13 at 04:57

cbayram

2,259
11
9

Regular expression to match a string in incorrect case

3 Answers3