Perhaps this will do what you require:

open IN,  '<', 'test.txt' or die "Can't open 'test.txt' $!";
open OUT, '>', 'test.out' or die "Can't open 'test.out' $!";

while ( <IN> ) {
    next unless /\S/;
    tr/ \t/ /s;
    print OUT;  # Updated -- thanks Narveson
    }

close IN;
close OUT;
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