Substitute and store in another scalar [duplicate]

Question

How can I use $_ to store my string, and then use another scalar variable to store the substituted string such that I have both the copies. Do we have a modifier to copy the default argument in some another variable?

#! /usr/bin/perl/
use warnings;
use strict;

$_ = "X is a good boy. X works daily and goes to school. X studies for 12 hours daily \n";

s/X/Sam/g;
print $_, "\n";

What I want in the end is the original $_ and the substituted string as well.

Edit: I used

my $new = s/X/Sam/gr

But I get an error related to build, and it doesnt solve the issue. I am using version 5.10.1

perl --version

This is perl, v5.10.1 (*) built for x86_64-linux-thread-multi

Answer 1

One way, of course, is to first copy the original and make the substitution on the copy.

( my $new = $_ ) =~ s/X/Sam/g;

Another way is to use the /r modifier (introduced in v5.14). It returns the new string, leaving the original unchanged

my $new = $_ =~ s/X/Sam/gr;

Find it in perlop, under the bullet "s/PATTERN/REPLACEMENT/msixpodualngcer".

Note interesting uses in Examples. With /r you can also do

my $new = s/X/Sam/gr;

---

Since /r modifier is available on v5.14 or newer you may want to have use 5.014;, not allowing the code to run at all on older Perls and documenting the required version. On the other hand, without that on an older Perl you get a specific error, with the location where unavailable features are used.