bug#48038: 26.3; Incorrect syntax highlighting in perl-mode

[Morten Welinder <mwelinder@gmail.com>]

1. Start "emacs -Q" and create a buffer "foo.pl" with the contents

my %h = (foo => 1,
     q_foo => 2,
     );

2. Notice that "q" is coloured black and "_foo" and everything thereafter is
    coloured red.  Expected is that the whole key is black and that
the subsequent
   text is not affected.

Note: just loading a file with the above contents is not enough.  The
problem appears to happen during typing, specifically at [Enter] after
"2,".

A workaround is to change "_" to be a word character, but that comes
with changes
in word movement commands thereby upsetting ancient muscle memory.

Morten






In GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.14)
 of 2020-03-26, modified by Debian built on lcy01-amd64-020
Windowing system distributor 'The X.Org Foundation', version 11.0.12009000
System Description:    Linux Mint 20.1

Recent messages:
Quit
completing-read-default: Command attempted to use minibuffer while in minibuffer
Quit
C-x C-g is undefined
Quit [2 times]
(New file)
kill-line: End of buffer [3 times]
Saving file /home/welinder/foo.pl...
Wrote /home/welinder/foo.pl
Mark set
previous-line: Beginning of buffer
Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --enable-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --build
 x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
 --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --with-x=yes
 --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -fdebug-prefix-map=/build/emacs-mEZBk7/emacs-26.3+1=. -fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS LIBSYSTEMD LCMS2

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Perl

Minor modes in effect:
  shell-dirtrack-mode: t
  diff-auto-refine-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny rfc822 mml mml-sec epa
derived epg epg-config gnus-util rmail rmail-loaddefs mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
make-mode add-log cl-extra help-mode edmacro kmacro m4-mode dabbrev
dired dired-loaddefs thingatpt grep compile python tramp-sh tramp
tramp-compat tramp-loaddefs trampver ucs-normalize shell pcomplete
parse-time format-spec advice auth-source cl-seq eieio eieio-core
cl-macs eieio-loaddefs password-cache json map seq byte-opt gv bytecomp
byte-compile cconv comint ring ansi-color misearch multi-isearch vc-git
diff-mode easy-mmode perl-mode cc-mode cc-fonts easymenu cc-guess
cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
cl-loaddefs cl-lib elec-pair time-date mule-util tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow isearch timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 327211 31035)
 (symbols 48 26835 5)
 (miscs 40 248 2187)
 (strings 32 48939 3513)
 (string-bytes 1 1559376)
 (vectors 16 49625)
 (vector-slots 8 1598228 187380)
 (floats 8 75 458)
 (intervals 56 15342 59)
 (buffers 992 29))