1. In a temporary directory, say ~/tmp/, get latest cperl-mode.el from

https://github.com/emacs-mirror/emacs/blob/master/lisp/progmodes/cperl-mode.el
   I used the Jul-28-2025 version

https://github.com/emacs-mirror/emacs/blob/cef4302d309e26c2191821ba998518fb89fff54e/lisp/progmodes/cperl-mode.el

2. cd ~/tmp

3. emacs -Q -L .           # Using emacs 30.1

4. M-x byte-compile-file RET cperl-mode.el RET

5. C-x C-f foo.pl

   C-x h   # select all of foo.pl
   C-M-\   # indent foo.pl

Here's the indented foo.pl:

# -*- mode: cperl -*-
my $str =~ s/^
    (Field1: [^\n]+) \s*
  Field2: \s* (\S+) \s*
            //xsm;

Notice that the regexp is not indented nicely. I would expect "Field2 ..."
to be aligned under
"(Field...)":

  my $str =~ s/^
               (Field1: [^\n]+) \s*
               Field2: \s* (\S+) \s*
               //xsm;


In GNU Emacs 30.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
 cairo version 1.16.0) of 2025-04-04, modified by Debian built on sbuild
Windowing system distributor 'The X.Org Foundation', version 11.0.12101006
System Description: Debian GNU/Linux 12 (bookworm)

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/30.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/30.1/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/libexec --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-libsystemd
 --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/30.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/30.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --with-cairo
 --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
 'CFLAGS=-g -O2
 -ffile-prefix-map=/build/reproducible-path/emacs-30.1+1=.
-fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NATIVE_COMP
NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

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

Major mode: CPerl

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-regexp-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/home/ciolfi/tmp/cperl-mode hides
/usr/share/emacs/30.1/lisp/progmodes/cperl-mode

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs cl-lib sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils compile
text-property-search comint subr-x ansi-osc ansi-color ring comp-run
bytecomp byte-compile comp-common cperl-mode rx facemenu rmc iso-transl
tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd
touch-screen tool-bar dnd fontset image regexp-opt fringe tabulated-list
replace newcomment text-mode lisp-mode prog-mode register page tab-bar
menu-bar rfn-eshadow isearch easymenu timer select scroll-bar mouse
jit-lock font-lock syntax font-core term/tty-colors frame minibuffer
nadvice seq simple cl-generic indonesian philippine 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 emoji-zwj charscript charprop
case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting cairo gtk x-toolkit xinput2 x multi-tty move-toolbar
make-network-process native-compile emacs)

Memory information:
((conses 16 84401 12096) (symbols 48 7366 0) (strings 32 20464 1856)
 (string-bytes 1 700197) (vectors 16 11848)
 (vector-slots 8 163636 10525) (floats 8 26 34) (intervals 56 418 0)
 (buffers 992 12))