Is it possible to use repetition within a Regular Expression Substitution?

greatwazzoo has asked for the wisdom of the Perl Monks concerning the following question:

Is it possible to use repetition within a Regular Expression Substitution? Apologies if this is a simple solution, but I've done some digging and haven't been able to find an answer.
I have a simple logfile, that works with an existing script, however sometimes I receive an improperly formatted file.
What I'm trying to do is a simple commandline perl to replace a line that starts with 40 hyphens "-", and I need to replace it with 80 asterisks.
instead of typing the 80 asterisks is it possible to use the "x" repetition within the substitution?
e.g.

perl -pi -e 's/^\-{40,40}^M*$/((\*) x 80)/' logfile
[download]

that is the "\*" x 80 , within the regular expression,..or something to that effect.,
Thanks

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Re: Is it possible to use repetition within a Regular Expression Substitution? by shmem (Chancellor) on Mar 20, 2010 at 01:13 UTC
Almost... use the 'e' modifier to the regex: `perl -pi -e 's/^\-{40,40}^M$/"" x 80/e' logfile` [download] whih means that the substitution part is treated as expresion and its result is substituted.	[reply] [d/l]
Re: Is it possible to use repetition within a Regular Expression Substitution? by ikegami (Patriarch) on Mar 20, 2010 at 02:45 UTC
^M? is that a literal Carriage Return? It might be more readable to use \r, \015 or \x0D instead. And then there's "`\-`" which can be simplified to just "`-`". Finally, "`{40,40}`" can be written as "`{40}`". `/^-{40}\r*$/` [download]	[reply] [d/l] [select]
Re: Is it possible to use repetition within a Regular Expression Substitution? by ww (Archbishop) on Mar 20, 2010 at 01:30 UTC
Update: ~~Not directly, by any means I've found (nor by any explicitly sanctioned by~~ </update> shmem found a "direct" means... but see Friedl, Mastering Regular Expressions, anyway. ~~However:~~ TIMTOWTDI: `#!/usr/bin/perl use strict; use warnings; # 829735 my $replacement =""x80; print "$replacement \n"; my @logfile = <DATA>; for my $logfileline(@logfile) { $logfileline =~ s\|^\-+\|$replacement\|; print "$logfileline \n"; } __DATA__ phoney content -------------------------------------- more dummy stuff` [download] which appears to do what you want: `ww@GIG:~/pl_test$ perl 829735.pl ******************************************************************* +****** phoney content ****************************************************************** +******** more dummy stuff ww@GIG:~/pl_test$` [download] NB: `\-+` in the regex because I'm too lazy to count the hyphens. :-)	[reply] [d/l] [select]
Re: Is it possible to use repetition within a Regular Expression Substitution? by JavaFan (Canon) on Mar 20, 2010 at 13:14 UTC
I would write that as: `my $stars = "" x 80; s/^-{40}\cM$/$stars/;` [download] Or even `my $stars = "" x 80; my $dashes = "-" x 40; s/^$dashes\cM$/$stars/;` [download]	[reply] [d/l] [select]
Re: Is it possible to use repetition within a Regular Expression Substitution? by Anonymous Monk on Mar 20, 2010 at 03:39 UTC
`perl -pi -e 'BEGIN{$x = "" x 80} s/^-{40}^M$/$x/' logfile` [download]	[reply] [d/l]