(defun perlish-fix-regexps (regexp)
  "Simple translation of a perlish REGEXP to an emacs one."
  (let ( (new-pattern regexp) )
    (setq new-pattern (replace-regexp-in-string "(" "\\\\(" new-patter
+n))
    (setq new-pattern (replace-regexp-in-string ")" "\\\\)" new-patter
+n))
    (setq new-pattern (replace-regexp-in-string "|" "\\\\|" new-patter
+n))
    (setq new-pattern (replace-regexp-in-string "\\\\\"" "\"" new-patt
+ern))
    new-pattern))

(perlish-fix-regexps "(.*?)")
(perlish-fix-regexps "(ha|ho)")
(perlish-fix-regexps "\"[ \t]*(.*?)[ \t]*\"")

(defun perlish-match (string pattern)
  "Apply the perlish PATTERN to STRING, returns capture from first gro
+up of parens."
  (let (
        (emacs-pattern (perlish-fix-regexps pattern))
        (found  "")
        )
    (if (string-match emacs-pattern string)
        (setq found (match-string 1 string))
      )
    ))

(perlish-match "ha, ha, ho, ho!" "(ha|ho)" )
(perlish-match
   "  \"  quote  \"  "
   "\"[ \t]*(.*?)[ \t]*\"")
[download]

I know most of this and just experimented a little bit, it's a hack but I thinks it's a good start 8)

Of course substituting \\ as \0 is only a temporarily solution ...

$\="\n";
 
#--- flags  
my $flag_interactive; # true => no extra escaping of backslashes
 
 
my $RE='\w*(a|b|c)\d\(';
$RE='\d{2,3}';
 
print $RE;
 
#--- hide pairs of backslashes
$RE=~s#\\\\#\0#g;
 
 
#--- toggle escaping of 'backslash constructs'
my $bsc='(){}|';
$RE=~s#[$bsc]#\\$&#g;  # escape them once
$RE=~s#\\\\##g;        # and erase double-escaping
 
 
#--- replace character classes
my %charclass=(
        w => 'word' ,   # TODO: emacs22 already knows \w ???
        d => 'digit',
        s => 'space'
       );
 
my $kc=join "|",keys %charclass;
$RE=~s#\\($kc)#[[:$charclass{$1}:]]#g; 
 
 
 
#--- unhide pairs of backslashes
$RE=~s#\0#\\\\#g;
 
#--- escape backslashes for elisp string
$RE=~s#\\#\\\\#g unless $flag_interactive;
 
 
print $RE;
[download]

Do you see any problems?

this version translates your example well, IMHO there are only the two mentioned TODOs left to be covered.

/usr/bin/perl -w /tmp/plre2el.pl 
Perlcode: "(.*?)"
Elispcode: \"\\(.*?\\)\"
[download]

use strict;
use warnings;
 
 # version 0.2
 
 $\="\n";
 
 #--- flags  
 my $flag_interactive; # true => no extra escaping of backslashes
 
 
 my $RE='\w*(a|b|c)\d\(';
 $RE='\d{2,3}';
 $RE='"(.*?)"';
 
 print "Perlcode: $RE";
 
 #--- hide pairs of backslashes
 $RE=~s#\\\\#\0#g;
 
 # TODO check for suitable long "hidesequence" instead of a simple \0
 
 #--- TODO normalisation of needless escaping
 # e.g.  from /\"/ to /"/, since it's no difference in perl but might 
+confuse elisp
 
  
 #--- toggle escaping of 'backslash constructs'
 my $bsc='(){}|';
 $RE=~s#[$bsc]#\\$&#g;  # escape them once
 $RE=~s#\\\\##g;        # and erase double-escaping
 
 
 
 #--- replace character classes
 my %charclass=(
         w => 'word' ,   # TODO: emacs22 already knows \w ???
         d => 'digit',
         s => 'space'
        );
 
 my $kc=join "|",keys %charclass;
 $RE=~s#\\($kc)#[[:$charclass{$1}:]]#g; 
 
 
 
 #--- unhide pairs of backslashes
 $RE=~s#\0#\\\\#g;
 
 #--- escaping for elisp string
 unless ($flag_interactive){
   $RE=~s#\\#\\\\#g; # ... backslashes
   $RE=~s#"#\\"#g;   # ... quotes
 }
 
 
 print "Elispcode: $RE";
[download]

Cheers Rolf

Please note: xemacs knows "Raw Strings" where escaping is not neccessary, but I doubt that normal Perl RE syntax can be used from within Gnu Emacs Lisp because of the quoting problem, so the conversion can in general only be done with perl!

UPDATE:

-TODO: Just noticed that i still need a special treatment for escape sequences like \t and \n. I'll add this tomorrow.

last version re_pl2el.pl

Read more... (2 kB)

This looks very useful. Has it been updated or put somewhere like CPAN or github?