$ perl -E 'my $x = "2.X"; my ($y, $z) = ($x =~ /^(\d+)(.*)$/); say $x; say ++$y . $z'
2.X
3.X

##</code><code>##

$ perl -E 'my $x = "02.X"; my ($y, $z) = ($x =~ /^(\d+)(.*)$/); say $x; say ++$y . $z'
02.X
03.X

##</code><code>##

$ perl -E 'say for sort qw{1.X 9.X}'
1.X
9.X

$ perl -E 'say for sort qw{1.X 9.X 10.X}'
1.X
10.X
9.X

$ perl -E 'say for sort qw{01.X 09.X 10.X}'
01.X
09.X
10.X

##</code><code>##

U+00DC LATIN CAPITAL LETTER U WITH DIAERESIS