Don't be silly, you can't install John McNamara ;-)
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John.

Could you explain how this is possible?

I've grepped through CPAN/*.pm, but I've failed to find any relevant code.

This is more artifice than obfuscation.

The "& _ x ord $ ;" code is used to convert my lowercase PerlMonks ID jmcnamara to my uppercase CPAN directory JMCNAMARA. I could have used uc but I thought that I should put in a little effort. ;-)

    # The following are equivalent

    perl -MCPAN -e 'install jmcnamara & _ x ord $ ;'

    perl -MCPAN -e 'install "jmcnamara" & ( "_" x ord($;) )'

    perl -MCPAN -e 'install "jmcnamara" & ( "_" x 28 )'

    # With bitwise string "&" the longer string is truncated
    # to the length of the shorter string. Therefore:

    perl -MCPAN -e 'install "jmcnamara" & ( "_" x 9 )'

    perl -MCPAN -e 'install "jmcnamara" & "_________"'

    perl -MCPAN -e 'install JMCNAMARA'
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Running this will cause CPAN to generate an error because you are trying to install a directory instead of module (or bundle). This helpfully translates my PerlMonks name into my real name. Here is the output as seen through tail -l.     Don't be silly, you can't install John McNamara ;-)

This error message is buried in CPAN.pm.

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John.