Newcomers to Perl - beware!   When you read in a line in using  $input = <STDIN>;, what you read includes a new line sequence.  If you then use the variable $input to be a file name, it's a very curious file name with the new line sequence on the end of it!

Easy options - use either the chomp function or the chop function to remove the new line sequence;  better option if you're trying to "bullet proof" your code - match it against a regular expression to ensure that the file name  given isn't an attempted hack  

From my mailbag: ....
"Can you help me with this problem. I need to perform some actions on a dos textfile on a unix platform. I want to chomp the cr/lf. When I do that the function works not correct anymore."

Err - technically it does work correctly - it removes the Unix end of line character (which is just a new line) leaving the carriage return that dos also uses on the end of the string.

I would suggest you replace your chomp with
     $line =~ s/\s+$//;
which will strip off all trailing white spaces - tabs, spaces, new lines and returns as well.   This makes your code work on Unix and Linux whether the input file is from Windows or from Unix.   As a side effect, it also removes any trailing whitespace on each line which is usually but not always an advantage.

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