Newbie Perl syntax questions

I am not a Perl programmer, but have inherited some Perl code that is running on our server.  I am familiar with Pascal and BASIC, so I know how to program.  I'm trying to document the source code and did not want to spend hours googling the web hoping to find Perl syntax guides.  Perhaps someone would be kind enough to explain in simple English what the following lines of code do?   What follows is not the exact source code, but lines of code snatched here and there which I do not understand. What exactly does each section do (each section separated by a blank line)

umask( 022 );

$| = 1;

my $Id;

chop;

$UPass = unpack( 'u', $UPass );

s/\$([a-zA-Z0-9_]+)/$Values{$1}/g;

$UserUniq = $_[0];
$UserStatus = $_[1];
$UserStep = $_[2];
$NumQuest = $_[3];

$UueRandomMask =~ s/\n//g;

$OneOfRightAnswers =~ s/^ *//;
$OneOfRightAnswers =~ s/ *$//;


$AnswerNum = 0;
foreach $OneOfAnswers ( split( / /, $RandomOrder ) ) {
      $AnswerNum++;
      $RealUserAnswer = $OneOfAnswers if( $UserAnswer == $AnswerNum );
};
$TextUserAnswer = $Answers{ $RealUserAnswer };
$RightAnswers{ $QuizRightAnswer } = 1;


if( m/^Q:/ ) {
      $CurrentQuestion++;
      last if( $CurrentQuestion > $UserStep );
};

...
    } elsif( $CurrentQuestion == 0 && ! m/&:/ ) {
      s/\r//;
    };

$HtmlTitle = browser_escape( $Title );

my $string = shift;
$string =~ s/([<&"#%>])/sprintf ('&#%d;', ord ($1))/ge;

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