$ perl -Mstrict -Mwarnings -E '
    my $find = q{#define MYVERSION };
    my $flen = length $find;
    my @strings = (
        q{#define MYVERSION 11},
        q{#define MYVERSION 9},
        q{#define MYVERSION 99}
    );
    for (@strings) {
        say;
        substr($_, $flen) = substr($_, $flen) + 1;
        say;
    }
'
#define MYVERSION 11
#define MYVERSION 12
#define MYVERSION 9
#define MYVERSION 10
#define MYVERSION 99
#define MYVERSION 100