(I applied my own code style and removed unnecessary braces, using $_ instead of explicit loop variables may have worked and may be considered more 'perlish', but I don't want to think about which of my loop stomped on which others' $_ so I'm using explicit variables. Handles for files and dirs have been replaced with a simple $fh/$dh. If these aren't sufficient then that's a good indication one has to many of them open at the same time. It also caught a bug where i was referring to $directory instead of $path.) 
#! /usr/bin/perl

use strict;
use warnings;

# $ERRNO instead of $! amongst other stuff
use English                    qw( -no_match_vars );

my $path = "./IN/";
my $string = 'ABC';
my @filesWithString;

opendir my $dh, $path
  or die "Can not open $path: $ERRNO";

FILE:
while (my $file = readdir $dh) {

    # ignore 'hidden' files and ., ..
    if ($file =~ m/^\./) {
        next FILE;
    }

    # opendir and this should be replace with File::Find
    # makes relocationg the perl script to a different directory
    # much easier
    my $filename = $path . $file;

    # always check return value for open, close
    open my $fh, '<', $filename
      or die "Can not open '$filename': $ERRNO";

    # keep track of current line number for nice message
    my $linecount = 1;

    LINE:
    while (my $line = <$fh>) {

        # encase $string in \Q \E in case it contains regexp metachara
+cters
        # (remove this if you actually want to use metachars)
        if ($line =~ m/\Q$string\E/) {
            print "Found string '$string' in file $filename (line $lin
+ecount)\n";

            push @filesWithString, $filename;

            # abort all further parsing - we already found the string
            last LINE;
        }

        $linecount++;
    }

    close $fh
      or die "Can not close filehandle for '$filename': $ERRNO";

}
closedir $dh
  or die "Can not close $path: $ERRNO";

for my $file (@filesWithString) {
    my $newName = $file . '.ABC.txt';

    print "Renaming $file to $newName\n";

    # uncomment this after debugging / verification
    #rename $file, $newName;
}

[download]

In reply to Re^2: Rename the text file WRT String by Monk::Thomas
in thread Rename the text file WRT String by reddevil420

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