concatenation eccentricity

[John McNally]

I had something similar to:

#set ( $a = "$b${c}foo.java" )
#set ( $d = "$b${c}.java" )

if $b=boy and $c=cat
this gives $a=boycatfoo.java and $d=boy${c}.java

 changing to 

#set ( $d = "${b}${c}.java" ) 
it works => $d = boycat.java

I have no problem with requiring the braces but not sure why it works
for $a but not $d.

John McNally