Try this

use strict;
my $arg = $ARGV[0];
open(IN,"$arg")||die("Can't open the input file for reading");
undef $/;
my $str = <IN>;
close(IN);

$/="\n";
print ("\nDo u want to Change Example to Uppercase:");
$value = <STDIN>;
chomp($value);

if ($value=~/^y$/){
$str=~s/\b(example)\b/uc($1)/gei;
}

open (OUT,">$arg")||die("Can't open the output file for writing");
print OUT $str;
close(OUT);
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