Regex: Extracting the case insensitive string and printing on the output

rockstar99 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Gurus, I have a program which searches a for a string in within a target string and prints yes or no if the string is present or not. The following is how code looks like

 
$mytarget = "I am a perl program";
$mystring = "Perl";
if ($mytarget =~ m/$mystring/i)
     {       
         print "It matches\n";   
     }   
  else {       
         print "It doesn't match\n";    
    }
[download]

This prints "It matches" though the case does not match as I am using regex m//i . Now how can I actually fetch the actual string "perl" from $mytarget and print on the screen,

"The actual string in the target is : perl". Thanks in advance

Comment on Regex: Extracting the case insensitive string and printing on the output Select or Download Code

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Re: Regex: Extracting the case insensitive string and printing on the output by Ratazong (Monsignor) on Nov 28, 2011 at 10:10 UTC
Use `( )` to grab what you want. The result(s) will be in the special variables $1, $2, ... `if ($mytarget =~ m/($mystring)/i) { print "It matches $1\n"; }` [download] see perlretut (section on extracting matches).	[reply] [d/l] [select]
Re^2: Regex: Extracting the case insensitive string and printing on the output by rockstar99 (Novice) on Nov 28, 2011 at 10:13 UTC
Thanks Ratazong. Made that simple. :)	[reply]
Re: Regex: Extracting the case insensitive string and printing on the output by trizen (Hermit) on Nov 29, 2011 at 00:54 UTC
I recommend to use ${^MATCH}. It is much faster than capturing to $1 `Benchmark: timing 2222234 iterations of code_1, code_2... code_1: 4 wallclock secs ( 4.03 usr + 0.00 sys = 4.03 CPU) @ 55 +1422.83/s (n=2222234) code_2: 2 wallclock secs ( 2.27 usr + -0.01 sys = 2.26 CPU) @ 98 +3289.38/s (n=2222234) Rate code_1 code_2 code_1 551423/s -- -44% code_2 983289/s 78% --` [download] ... and don't forget about quotemeta or \Q \E when matching $strings. `$mytarget = "I am a perl program"; $mystring = "Perl"; if ($mytarget =~ m/\Q$mystring\E/i) { print "It matches: ${^MATCH}\n"; } else { print "It doesn't match\n"; }` [download]	[reply] [d/l] [select]
Re^2: Regex: Extracting the case insensitive string and printing on the output by AnomalousMonk (Archbishop) on Nov 29, 2011 at 08:16 UTC
I recommend to use ${^MATCH}. Always use the /p regex modifier when using `${^MATCH}` and friends. The use of `${^MATCH}` may appear to work without the /p modifier, but this is only fortuitous. Quoth perlvar (emphasis added): ${^MATCH} This is similar to $& ($MATCH) except that it does not incur the performance penalty associated with that variable, and is only guaranteed to return a defined value when the pattern was compiled or executed with the "/p" modifier.	[reply] [d/l] [select]
Re: Regex: Extracting the case insensitive string and printing on the output by ansh batra (Friar) on Nov 28, 2011 at 10:08 UTC
i is for ignore case remove i and then run Edit: $& can be used to get the matched pattern	[reply]