how to give a path address in a code using perl

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Perl

use strict;
use warnings;

my $file=register.txt;
#read the data from file
 
 my $data= slurp($file);
#print the string data
print $data;

string $data = FILE.ReadAllText(path);
$data = data.Replace(" ",",");
file.WriteAllText(path,data);

#we will just print the data

print "$data\n";

close($data);

(this is my code in that howto address the path ?
my given data like this 20000 lines are there to convert

arunav 1236
askjasi 25986
sdhfuis 26897
krotri  6598548

I want output

arunav,1236
askjasi,25986
sdhfuis,26897
krotri ,6598548

could please one help me