Thanks; I can reproduce this on master. Calling word-at-point on "2" shows the same problem (it doesn't include "1").
The problem seems to be a custom syntax-table property that cperl-mode puts on "1".

Clément.

On 2016-07-28 20:05, Vincent Lefevre wrote:
> 
> 1. Under X Window (so that Emacs uses its own interface), open
> a file containing:
> 
> # -*- mode: cperl -*-
> 
> tr/ABCDE/12345/;
> 
> 2. Double-click over "4".
> 
> Only "2345" is selected, instead of "12345".
> 
> 
> 
> In GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.20.3)
>  of 2016-05-07 on zira, modified by Debian
> Windowing system distributor `The X.Org Foundation', version 11.0.11804000
> System Description:	Debian GNU/Linux stable-updates (sid)
> 
> 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 --with-pop=yes
>  --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
>  --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
>  --libexecdir=/usr/lib --localstatedir=/var/lib
>  --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
>  --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
>  --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
>  'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
>  -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
>  -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'
> 
> Important settings:
>   value of $LC_COLLATE: POSIX
>   value of $LC_CTYPE: en_US.UTF-8
>   value of $LC_TIME: en_DK
>   value of $LANG: POSIX
>   locale-coding-system: utf-8-unix
> 
> Major mode: Lisp Interaction
> 
> Minor modes in effect:
>   display-time-mode: t
>   show-paren-mode: t
>   tooltip-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
>   column-number-mode: t
>   line-number-mode: t
>   transient-mark-mode: t
> 
> Recent messages:
> Loading cjk-enc...done
> Loading /etc/emacs/site-start.d/50latex-cjk-common.el (source)...done
> Loading /etc/emacs/site-start.d/50latex-cjk-thai.el (source)...done
> Loading /etc/emacs/site-start.d/50psvn.el (source)...done
> Loading /etc/emacs/site-start.d/50python-docutils.el (source)...done
> Loading /etc/emacs/site-start.d/50rnc-mode.el (source)...done
> Loading /etc/emacs/site-start.d/50texlive-lang-english.el (source)...done
> Loading /home/vinc17/share/emacs/site-lisp/mutteditor.el (source)...done
> Loading time...done
> For information about GNU Emacs and the GNU system, type C-h C-a.
> 
> Load-path shadows:
> /usr/share/emacs/24.5/site-lisp/debian-startup hides /usr/share/emacs/site-lisp/debian-startup
> /usr/share/emacs24/site-lisp/cmake-data/cmake-mode hides /usr/share/emacs/site-lisp/cmake-mode
> /usr/share/emacs/site-lisp/rst hides /usr/share/emacs/24.5/lisp/textmodes/rst
> /usr/share/emacs24/site-lisp/latex-cjk-thai/thai-word hides /usr/share/emacs/24.5/lisp/language/thai-word
> 
> Features:
> (shadow sort gnus-util mail-extr warnings emacsbug message format-spec
> rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse
> rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
> ietf-drums mm-util help-fns mail-prsvr mail-utils time cus-start
> cus-load paren cc-styles cc-align cc-engine cc-vars cc-defs edmacro
> kmacro cl-loaddefs cl-lib time-date tooltip electric uniquify ediff-hook
> vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image
> regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode register
> page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
> font-lock syntax facemenu font-core frame cham georgian utf-8-lang
> misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
> greek romanian slovak czech european ethiopic indian cyrillic chinese
> case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer 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 make-network-process dbusbind
> gfilenotify dynamic-setting system-font-setting font-render-setting
> move-toolbar gtk x-toolkit x multi-tty emacs)
> 
> Memory information:
> ((conses 16 92575 4671)
>  (symbols 48 20397 0)
>  (miscs 40 45 93)
>  (strings 32 16037 4299)
>  (string-bytes 1 472568)
>  (vectors 16 10305)
>  (vector-slots 8 396942 4282)
>  (floats 8 70 229)
>  (intervals 56 231 6)
>  (buffers 960 12)
>  (heap 1024 37269 984))
> 
> 
> 
>