#!/usr/bin/perl -w

use strict;

my $SCU= 'C:/Users/Desktop/a.txt';


open(FILE, "<$SCU") || die "File not found";
my @lines = <FILE>;
close(FILE);

#my $copy = $_; 

my @newlines;
foreach(@lines) {
   push @newlines, s/<test>/xyz/rg for @lines;
}

open (FILE, ">", "$SCU") or die "Could not open file $SCU: $!";

print FILE @newlines;
close(FILE);