C:\Temp>perl -CiO -i.bak -pe "s{(?<=[/\\]ReleaseDLL)(?=[/\\])}{32} if m{^\s*<(?:Out|Int)Dir>}" fred.vcxproj

C:\Temp>diff fred.vcxproj.bak fred.vcxproj
9,10c9,10
<     <OutDir>.\../../products/bin/ReleaseDLL\</OutDir>
<     <IntDir>.\ReleaseDLL\</IntDir>
---
>     <OutDir>.\../../products/bin/ReleaseDLL32\</OutDir>
>     <IntDir>.\ReleaseDLL32\</IntDir>
15,16c15,16
<     <OutDir>.\../../products/bin/ReleaseDLL\</OutDir>
<     <IntDir>.\ReleaseDLL\</IntDir>
---
>     <OutDir>.\../../products/bin/ReleaseDLL32\</OutDir>
>     <IntDir>.\ReleaseDLL32\</IntDir>

C:\Temp>od -h -N 3 fred.vcxproj
0000000000    EF  BB  BF
0000000003

C:\Temp>