I suggest printing both strings out with delimiters to see what they look like:

printf ']%s[\n', $string1;
printf ']%s[\n', $string2;
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The ]['s will make whitespace in the strings noticeable.

If you still don't see a difference, print the hex values of each byte in the string to see where it mismatches. And consider changing your system font if it turns out to be an I vs 1 thing or something similar.