That wording is incorrect. "=>" quotes anything on the left that looks like a valid (non-punctuation, user-definable) identifier name. And identifiers cannot start with a digit.

$ perl -Mstrict -e 'print foo => "\n"'
foo
$ perl -Mstrict -e 'print foo::bar => "\n"'
foo::bar
$ perl -Mstrict -e 'print foo:bar => "\n"'
syntax error at -e line 1, near "foo:"
Execution of -e aborted due to compilation errors.
$ perl -Mstrict -e 'print 0foo => "\n"'
syntax error at -e line 1, near "0foo"
Execution of -e aborted due to compilation errors.
$ perl -Mstrict -e "print foo'bar => qq'\n'"
foo::bar
$ perl -Mstrict -e "print foo''bar => qq'\n'"
Bad name after foo' at -e line 1.
$ perl -Mstrict -e "print foo'baz'bar => qq'\n'"
foo::baz::bar
$
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