Your problem is that the  while (<F>) will only read a single line, and your  emp and /emp do not occure on the same line.

To do what you are trying to do here you could use  local $/; before the  while, to make Perl slurp in the whole data as one line. You will also need to alter the regex to use the s option ( which also has an extra paren at the end ):

$_ =~m/(<emp>.*<\/emp>)/s;
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The /s says (simplified) to treat the whole string as a single line -- don't stop patterns at the newlines.

Of course if you are doing more than just toy-work with XML you might want to check out www.cpan.org and check out the libraries available there.