Basic debugging checklist says to find out what perl thinks of your program use B::Deparse, like  perl -MO=Deparse,-p ...

So

$ perl -MO=Deparse,-p -wlne " ! /def/ and print qq{$_}; "
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: while (defined(($_ = <ARGV>))) {
    chomp($_);
    (/def/ or print("$_"));
}
-e syntax OK
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