ReadEnvStr $APPLANGUAGE

You might like to try the environment variable PortableApps.comLocaleWinName. This produces things like LANG_ENGLISH, LANG_PORTUGUESE.

ReadEnvStr $0 PortableApps.comLocaleWinName
StrCpy $APPLANGUAGE $0 "" 5

$APPLANGUAGE will be e.g. ENGLISH, PORTUGUESE. If you find any instances where the PortableApps.comLocaleWinName is different, then you can do a StrCmp/StrCpy thing. Try LogicLib though, it's much easier:

${IfThen} $APPLANGUAGE == SPANISHINTERNATIONAL ${|} StrCpy $APPLANGUAGE Spanish ${|}