You are matching only whitespace in parens (\s eq. whitespace). What you want is

$input = "(here is words or numbers or dates) information starts here 
+etc...";

if($input =~ s/^\(([^\)]+)\)\s*// )
{
  print "deleted:$1\n";
  print "rest:$input\n"
}
#output: 
# deleted:here is words or numbers or dates
# rest:information starts here etc...
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