Importing username into Logon Page - O365 SAML

Seems to be that the expression string contains some extra (invisible) characters when copy-pasted from the site:

    $ od -Xc
expr {[string first “%40” [mcget {session.server.landinguri}]] – 1}
0000000          72707865        735b7b20        6e697274        69662067
           e   x   p   r       {   [   s   t   r   i   n   g       f   i
0000020          20747372        259c80e2        80e23034        6d5b209d
           r   s   t       “  **  **   %   4   0   ”  **  **       [   m
0000040          74656763        65737b20        6f697373        65732e6e
           c   g   e   t       {   s   e   s   s   i   o   n   .   s   e
0000060          72657672        6e616c2e        676e6964        7d697275
           r   v   e   r   .   l   a   n   d   i   n   g   u   r   i   }

The APM parser does not give much error messages, but refuses to accept the entry. Try to type the expression by hand instead of copy-pasting from the source web site. Also note that the quotation marks around should be straight ( "username" ), not curved ( “username=” ).