Use the specified perl.
--- netsurf/Makefile.orig	2020-05-24 16:35:22.000000000 -0500
+++ netsurf/Makefile	2021-04-13 21:34:45.000000000 -0500
@@ -922,13 +922,13 @@
 
 # split fat messages into properties files suitable for uploading to transifex
 messages-split-tfx:
-	for splitlang in $(FAT_LANGUAGES);do perl ./utils/split-messages.pl -l $${splitlang} -f transifex -p any -o Messages.any.$${splitlang}.tfx resources/FatMessages;done
+	for splitlang in $(FAT_LANGUAGES);do $(SPLIT_MESSAGES) -l $${splitlang} -f transifex -p any -o Messages.any.$${splitlang}.tfx resources/FatMessages;done
 
 # download property files from transifex
 messages-fetch-tfx:
-	for splitlang in $(FAT_LANGUAGES);do $(RM) Messages.any.$${splitlang}.tfx ; perl ./utils/fetch-transifex.pl -w insecure -l $${splitlang} -o Messages.any.$${splitlang}.tfx ;done
+	for splitlang in $(FAT_LANGUAGES);do $(RM) Messages.any.$${splitlang}.tfx ; $(PERL) ./utils/fetch-transifex.pl -w insecure -l $${splitlang} -o Messages.any.$${splitlang}.tfx ;done
 
 # merge property files into fat messages
 messages-import-tfx: messages-fetch-tfx
-	for tfxlang in $(FAT_LANGUAGES);do perl ./utils/import-messages.pl -l $${tfxlang} -p any -f transifex -o resources/FatMessages -i resources/FatMessages -I Messages.any.$${tfxlang}.tfx ; $(RM) Messages.any.$${tfxlang}.tfx; done
+	for tfxlang in $(FAT_LANGUAGES);do $(PERL) ./utils/import-messages.pl -l $${tfxlang} -p any -f transifex -o resources/FatMessages -i resources/FatMessages -I Messages.any.$${tfxlang}.tfx ; $(RM) Messages.any.$${tfxlang}.tfx; done