My question is, why is the assignment operator '=>' in the first 'print' statement here interpreted as a dot and not as a comma.

It isn't. It is being interpreted as a comma that quotes the string on its left hand side. B::Deparse shows what going on:

    perl -MO=Deparse  -e 'print nono => "1";'
    print 'nono', '1';
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In the second example strict doesn't care about the bareword nono (see below). Nevertheless, this would generate a warning with -w.

In the last example the bareword looks like a filehandle. And since a filehandle shouldn't have a comma after it in a print statement the compiler, not strict, rejects it.

--
John.