tests: use $PERL instead of perl

* tests/core/ltl2tgba2.test, tests/core/ltldo.test,
tests/core/ltlfilt.test, tests/core/neverclaimread.test,
tests/core/parseaut.test, tests/sanity/bin.test: Here.

tests/core/ltl2tgba2.test

@@ -386,7 +386,7 @@ EOF
 ltlfilt -Fformulas/1 --stats='%f,%f,%>' |
 ltl2tgba -F-/2 --stats='%<,%<, %s,%t' |
     ltl2tgba -D -F-/2 --stats='%<,%<,%>, %s,%t' |
-    perl -p -e 's/$/\r/' |
+    $PERL -p -e 's/$/\r/' |
     ltl2tgba -B -F-/2 --stats='%<,%<,%>, %s,%t' |
     ltl2tgba -BD -F-/2 --stats='%<,%<,%>, %s,%t' |
     ltl2tgba -GD -F-/2 --stats='%<,%>, %s,%t' > output

tests/core/ltldo.test

@@ -169,7 +169,7 @@ grep "ltldo: failed to parse '2a'.*-n" err
 genltl --rv-counter=9 | ltldo ltl2tgba --stats='
 print("%[up]R + %[uc]R + %[sp]R + %[sc]R - %R\n");
 die if abs(%[up]R + %[uc]R + %[sp]R + %[sc]R - %R) > 0.02;' > code.pl
-perl code.pl
+$PERL code.pl
 
 # ltldo should not leave temporary files behind itself on errors
 ltldo -f a 'ltl2dstar --ltl2nba=spin:ltl2tgba@-DS' && exit 2

tests/core/ltlfilt.test

@@ -1,6 +1,6 @@
 #! /bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2013-2019 Laboratoire de Recherche et Développement de
+# Copyright (C) 2013-2020 Laboratoire de Recherche et Développement de
 # l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -475,7 +475,7 @@ run 0 ltlfilt -p --wring -u --nnf --relabel=pnn --define in >out
 diff exp out
 
 run 0 ltlfilt -0 in > out
-perl -i -pe 's/\0/@\n/g' out
+$PERL -i -pe 's/\0/@\n/g' out
 cat >exp <<EOF
 a & c & Xb@
 a & b & GF(a | c) & FG(a | c)@

tests/core/neverclaimread.test

@@ -297,7 +297,7 @@ grep input: stderr > stderrfilt
 diff stderrfilt expected-err
 
 # DOS-style new lines should have the same output.
-perl -pi -e 's/$/\r/' input
+$PERL -pi -e 's/$/\r/' input
 run 2 ../ikwiad -ks -XN input > stdout 2>stderr
 cat stderr
 grep input: stderr > stderrfilt

tests/core/parseaut.test

@@ -695,7 +695,7 @@ input:8.1-16.12: aborted input automaton
 EOF
 
 # DOS-style new lines should have the same output.
-perl -pi -e 's/$/\r/' input
+$PERL -pi -e 's/$/\r/' input
 autfilt --hoa input 2>stderr && exit 1
 cat stderr
 diff stderr input.exp
@@ -1135,7 +1135,7 @@ EOF
 diff expected input.out
 
 # DOS-style new lines should have the same output.
-perl -pe -e 's/$/\r/' input
+$PERL -pe -e 's/$/\r/' input
 autfilt --hoa input 2>stderr && exit 1
 cat stderr
 diff stderr input.exp

tests/sanity/bin.test

@@ -1,7 +1,7 @@
 #! /bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2017 Laboratoire de Recherche et Développement de
-# l'Epita (LRDE).
+# Copyright (C) 2017, 2020 Laboratoire de Recherche et Développement
+# de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
 #
@@ -102,7 +102,7 @@ do
     # of the document string fall right into the rmargin.
     ARGP_HELP_FMT=rmargin=10000 \
     $top_builddir/bin/$binary --help > help-$binary.tmp
-    if ! perl -ne '/\n\s*\n(\s*-.*\n)/ && print("$1") && exit(1)' \
+    if ! $PERL -ne '/\n\s*\n(\s*-.*\n)/ && print("$1") && exit(1)' \
             -0777 help-$binary.tmp > help-err
     then
         echo "bin/$binary --help has options after blank line;" \