my ($key,$value);

  # DEBUG - BEGIN
  # your original regex
  $key= $line =~/;(.*)\s-\s/;
  $value= $line =~/\.\\(.*)-\d+\;/;
  print STDERR "key=<$key> value=<$value>\n";

  #outputs:  key=<1> value=<1>

  # the right way to get the value of the matched string in a
  # one liner - the parenthesis around ($key) and ($value) tell
  # perl that you want to return the array of matches, NOT the
  # number of matches.

  ($key) = $line =~/;(.*)\s-\s/;
  ($value) = $line =~/\.\\(.*)-\d+\;/;
  print STDERR "key=<$key> value=<$value>\n";

  # outputs: key=<perforcePLF.txt;//programfiles/documents/data/lookup/script_auth_pap.h> value=<\root\edit\perl\scripts\scripths\sec\inc\script_auth_pap.h>

  # The above still doesn't work because your key will include all
  # file names after the first ";" before " - " and not just the one
  # between the last ";" and " - ".  To get only the last one you need
  # a more restrictive regex, one that insures that there
  # are no ";" in your key, e.g. ([^;]*).  You also proabably
  # want to have a key with at least one character, so you should use
  # ([^;]+) rather than ([^;]*).

  ($key) = $line =~/;([^;]+)\s-\s/;
  ($value) = $line =~/\.\\(.*)-\d+\;/;

  # see comment below for why this is printed out to
  # STDERR and is followed by "last" 
  print STDERR "key=<$key> value=<$value>\n"; last;
  # DEBUG - END