regular expression search and replace

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

Hi Guys,

I'm trying to read 5 lines and replace any character which starts with a lower case to upper case. and replace the remaining characters to lower case. ex:

perlmonk is a gREat site. i loVE it.
in this case i expect the output to be:
Perlmonk is a great site. I love it.
[download]

I'm trying to use the following string replacement scheme. however, i don't see the replacement of [A-Z] being recognized as a keyword. But, it does recognize in the 1st case where i'm searching for a-zA-Z.

s/^\s*[a-zA-Z]/[A-Z]/g
[download]

Not sure if i'm missing some detail.

Thanks

Comment on regular expression search and replace Select or Download Code

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Re: regular expression search and replace by hippo (Archbishop) on Nov 18, 2014 at 17:55 UTC
Your replacement has to be something tangible, not a pattern. However you can use the `/e` modifier to execute code in the replacement. Combining this with a capture group works like this: `#!/usr/bin/perl use strict; use warnings; my $line = "perlmonk is a gREat site. i loVE it.\n"; print $line; $line = ucfirst lc $line; print $line; $line =~ s/(\. [a-z])/uc($1)/eg; print $line;` [download] Giving this output: `perlmonk is a gREat site. i loVE it. Perlmonk is a great site. i love it. Perlmonk is a great site. I love it.` [download] Be sure to have a good read of perlre as regexes and the s/// function are bedrocks of Perl. HTH, Hippo	[reply] [d/l] [select]
Re: regular expression search and replace by GrandFather (Saint) on Nov 18, 2014 at 19:55 UTC
Take a look at the transliteration operator (y/// or tr///) in Quote Like Operators. You'll need to scroll down a little of search for tr/. Perl is the programming world's equivalent of English	[reply]
Re^2: regular expression search and replace by heman (Novice) on Nov 18, 2014 at 23:49 UTC
Thanks guys :) All your inputs helped!! However, For some reason tr/ didn't work. It wouldn't recognize the \s in the replacement as space.	[reply]
Re^3: regular expression search and replace by GrandFather (Saint) on Nov 19, 2014 at 00:12 UTC
Go read the documentation again. tr/ doesn't do \s. It isn't really related to regular expression processing, it just happens to use the same binding operator (=~). Perl is the programming world's equivalent of English	[reply]
Re: regular expression search and replace by AnomalousMonk (Archbishop) on Nov 19, 2014 at 00:17 UTC
You seem to be parsing out sentences, and that's a tricky, natural language sort of thing to do, and perhaps not best done with regexen. If you can do it, the `\u \U \l \L` "interpolation control" (as I think of them) operators or escape sequences may come in handy for the transformations you want (see Quote and Quote-like Operators in perlop — and don't forget `\Q \E` too). You can avoid the `/e` regex modifier. With a very naive definition of a sentence pattern: `c:\@Work\Perl>perl -wMstrict -le "my $s = 'perlmonks IS a gREat site. dO you tHiNk SO? I loVE it!'; print qq{'$s'}; ;; my $senterm = '.?!'; my $sentence = qr{ \b [[:alpha:]] [^\Q$senterm\E]* [\Q$senterm\E] }xm +s; ;; $s =~ s{ ($sentence) }{\u\L$1}xmsg; print qq{'$s'}; " 'perlmonks IS a gREat site. dO you tHiNk SO? I loVE it!' 'Perlmonks is a great site. Do you think so? I love it!'` [download] An equivalent `/e` substitution would be `$s =~ s{ ($sentence) }{ ucfirst lc $1 }xmsge;` Is there any significant speed difference?	[reply] [d/l] [select]
Re: regular expression search and replace by ronin78 (Novice) on Nov 18, 2014 at 17:56 UTC
As I understand it, you want to capitalize the first letter in each sentence. You could do what you are trying to do above with a capture group (get the match and then uppercase it in your replace). However, you could also split the string into sentences, and then call uppercase on the first letter in the string and lowercase on the remainder.	[reply]