IE11 problem with Proxy.pac: Why does whitespace padded to a "if" statement get parsed as an End-of-file? Subsequent lines ignored.

Discovered apparent whitespace problem with IE11 using proxy.pac

We had an "If" statement in the middle of our proxy.pac which had whitespace padded at the end of the statement: 

if (host=="a.b.c.d")                 <CR/LF>return "DIRECT";<CR/LF>

The problem is that IE11 was then ignoring all subsequent lines in proxy.pac that followed the line with the 17 characters of  whitespace padding.

Is this a new bug introduced with IE11?

Our solution was to remove the extraneous whitespace at the end of the line, and the problem was resolved.

Why would IE11 have trouble with this whitespace added at the end of an "if" statement?