Is there documentation of the interactions between \Q, \U, \L and \E escapes in quoted strings?

I have seen Quote and Quote like Operators, but this doesn't describe how these escapes nest that I can see.

$ perl -e 'print "\Qab,cd\Uef,gh\Lij,kl\Emn,op\Eqr,st\Euv,wx\n";'
ab\,cdEF\,GHij\,klmn\,opqr,stuv,wx

[download]

One might expect

ab\,cdEF\,GHij\,klMN\,OPqr\,stuv,wx

[download]

update: or ab\,cdEF\,GHij\,klmn,opqr,stuv,wx.

update: or even ab\,cdEF\,GHIJ\,KLMN\,OPqr\,stuv,wx.

and

$ perl -e 'print "\Uab,cd\Qef,gh\Lij,kl\Emn,op\Eqr,st\Euv,wx\n";'
AB,CDEF\,GHij,klmn,opqr,stuv,wx

[download]

where one might expect

AB,CDEF\,GHij\,klMN\,OPQR,STuv,wx

[download]

Is there a rationale for how they nest and override each other? I find the inconsistency between \Q on the one hand and \U and \L on the other hand to be surprising.

In reply to Interactions of \Q, \U, \L and \E by ig

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