Of course, I suspect we're not going to be snobs about the suffixes, and can simply suggest that ...th is the standard "skipping suffix" for anyone who can't handle all four. That is:

    s:1th/pattern/string/;
    s:2th/pattern/string/;
    s:3th/pattern/string/;
    s:4th/pattern/string/;
    # etc.
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would be perfectly valid.

Alternatively, the rule might be that any suffix other than ...x means repetition:

    s:1um/pattern/string/;
    s:2ieme/pattern/string/;
    s:3itter/pattern/string/;
    s:4issimo/pattern/string/;
    # etc.
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