use strict;
use warnings;

sub findWords {
  my ($sText, $sEndSentence, $reStart, $reEnd)=@_;

  local $/=$sEndSentence;
  open(LONG_STRING, "<", \$sText) || die "Can't open string";
  while (my $line = <LONG_STRING>) {
    chomp $line;
    if (($line =~ $reStart) && ($line =~ $reEnd)) {
      print "match: $line\n";
    } else {
      print "no match: $line\n";
    }
  }
}

findWords("a b c.  Nullam est libero.Nullam est augue", '.'
          , qr(^\s*Nullam)
          , qr((?:libero|augue)\s*$));