An example:

c:\@Work\Perl\monks>perl -wMstrict -e
"use Data::Dump qw(dd);
 ;;
 $/ = qq{\n};
 ;;
 my $input = qq{OVERWRITTEN=key\r\n};
 ;;
 chomp $input;
 my ($value, $key) = split /=/, $input;
 dd $key;
 ;;
 my %hash = ($key, $value);
 print qq{The $key if not long enough is $hash{$key}};
"
"key\r"
 if not long enough is OVERWRITTEN
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See  $/ in perlvar and chomp.