qw is not really an operator, as it does all its work at compile time, and doesn't take an expression as argument, but only literal.

Anyway,

    qw{some string here};
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is more or less equivalent to:

    warn "Possible attempt to put comments in qw() list" 
          if q{some string here} =~ /#/ if $^W;
    warn "Possible attempt to separate words with commas"
          if q{some string here} =~ /,/ if $^W;
    split(' ', q{some string here});
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but then done at compile time.