INPUT FILE(p4diff.log) DATA:-
missing E:\qdepot_automation\addfiles.txt
same E:\qdepot_automation\AMSS\products\build\ms\files.data
same E:\qdepot_automation\AMSS\products\build\ms\build.cmd
missing E:\qdepot_automation\AMSS\products\build\textfiles.txt
same E:\qdepot_automation\AMSS\products\build\ms\lib.min

#!/usr/bin/perl -w 
use strict;  
use warnings;
use Cwd;
my $client_root="E:\\qdepot_automation";

my $perforce_root_dir="\/\/depot\/code";
my $input = <p4diff.log>; 
my $line;
#my ($client_root,$clientroot);

open(my $OUTPUT, '+>', "perforcefiles.txt") or die $!;
open my $DATA, '<', $input or die "could not open '$input' $!"; 

while ($line = <$DATA>)
{ 
   if ($line =~ /missing/)
   {
   $line =~s/\\/\//g; 
   $line =~s/$client_root/$perforce_root_dir/g; ###This line is not working,basically am not able to replace client_root with perforce_root_dir
   print "$line\n";
   print $OUTPUT $line;
   }
}
close OUTPUT;

OUTPUT:-
E:\qdepot_automation>perl deletefiles.pl
Name "main::OUTPUT" used only once: possible typo at deletefiles.pl line 25.
missing E:/qdepot_automation/addfiles.txt