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]

In reply to Re: Regex: Extracting the case insensitive string and printing on the output by trizen
in thread Regex: Extracting the case insensitive string and printing on the output by rockstar99

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