The other comments above are of course correct, but the insertion of a critical '?' (to prevent greedy matching) also seems to work:

$line="some text \(\)\xA1 file.txt";
if ($line =~ /(.+?)\s*\(\)\xA1\s*(.+\.txt)/) {
  $file = $1;
#  $file =~ s/\s*$//;
  print ("<a href=\"$2\">$file</a><br>\n");
}
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Tim