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$ perl -lwe 'use File::Spec::Functions; my $x="x"; require join("/",$x,$x)'
Can't locate x/x in @INC ...
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$ perl -lwe 'use File::Spec::Functions; my $x="x"; require catfile($x,$x)'
syntax error at -e line 1, near "require catfile("
Execution of -e aborted due to compilation errors.