userdiff/perl: tighten BEGIN/END block pattern to reject here-doc delimiters

A naive method of treating BEGIN/END blocks with a brace on the second
line as diff/grep funcname context involves also matching unrelated
lines that consist of all-caps letters:

	sub foo {
		print <<'EOF'
	text goes here
	...
	EOF
		... rest of foo ...
	}

That's not so great, because it means that "git diff" and "git grep
--show-function" would write "=EOF" or "@@ EOF" as context instead of
a more useful reminder like "@@ sub foo {".

To avoid this, tighten the pattern to only match the special block
names that perl accepts (namely BEGIN, END, INIT, CHECK, UNITCHECK,
AUTOLOAD, and DESTROY).  The list is taken from perl's toke.c.

Suggested-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4018-diff-funcname.sh

@@ -29,7 +29,7 @@ public class Beer
 }
 EOF
 sed 's/beer\\/beer,\\/' <Beer.java >Beer-correct.java
-cat >Beer.perl <<\EOF
+cat >Beer.perl <<\EOT
 package Beer;
 
 use strict;
@@ -56,6 +56,15 @@ sub finalround
 	print "99 bottles of beer on the wall.\n");
 }
 
+sub withheredocument {
+	print <<"EOF"
+decoy here-doc
+EOF
+	# some lines of context
+	# to pad it out
+	print "hello\n";
+}
+
 __END__
 
 =head1 NAME
@@ -76,7 +85,7 @@ Beer - subroutine to output fragment of a drinking song
 	song;
 
 =cut
-EOF
+EOT
 sed -e '
 	s/hello/goodbye/
 	s/beer\\/beer,\\/
@@ -138,6 +147,10 @@ test_expect_success 'perl pattern accepts K&R style brace placement, too' '
 	test_expect_funcname "sub finalround\$" perl
 '
 
+test_expect_success 'but is not distracted by end of <<here document' '
+	test_expect_funcname "sub withheredocument {\$" perl
+'
+
 test_expect_success 'perl pattern is not distracted by sub within POD' '
 	test_expect_funcname "=head" perl
 '

userdiff.c

@@ -74,7 +74,7 @@ PATTERNS("perl",
 		"(:[^;#]*)?"
 		"(\\{[ \t]*)?" /* brace can come here or on the next line */
 		"(#.*)?$\n" /* comment */
-	 "^[A-Z]+[ \t]*"	/* BEGIN, END, ... */
+	 "^(BEGIN|END|INIT|CHECK|UNITCHECK|AUTOLOAD|DESTROY)[ \t]*"
 		"(\\{[ \t]*)?" /* brace can come here or on the next line */
 		"(#.*)?$\n"
 	 "^=head[0-9] .*",	/* POD */