G'day Schmunzie,

Using this common alias of mine:

$ alias perlu
alias perlu='perl -Mstrict -Mwarnings -Mautodie=:all -Mutf8 -C -E'
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I get a length of six characters reported, and converting to uppercase has no apparent problems:

$ perlu 'say length("żłóBżE"); say uc("żłóBżE")'
6
ŻŁÓBŻE

Of course, I have no idea if your problem word was embedded in your script as literal Polish characters, \x{...} characters, or \N{...} characters. Perhaps you read it from the command line; perhaps it came from an input file.