Unary-"+" does not numify (or stringify). It's a no-op.

>perl -E"$_ = 'abc'; say +$_;"
abc

>perl -E"$_ = [qw( a b c )]; say @{ +$_ };"
abc
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It doesn't even influence context. Not even void!

>perl -E"sub f { say( ( (wantarray && 'list' ) // 'void' ) || 'scalar'
+ ); } +f(); $_=+f(); ()=+f();"
void
scalar
list
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What you said is the secondary effect is the only effect.