tr/// is better but all you needed to make your pseudocode real perl code was:

s/[^\040-\176]/ /g
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Note that the control chars are \000 - \037 so these are perhaps more direct:

tr/\000-\037/ /;    # best option for speed
s/[\000-\037]/ /g   # but this still works
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Note chr 32 dec 040 octal is the space so you were double spacing your spaces by starting at \041