Regular Expressions - Intermediate 3/10/01 [RegExpr.doc]
http://people.hofstra.edu/staff/harry_p_baya/perl/regExpr.htm

Special characters like "/" ... prefix with "\", e.g.    if $str =~ /<\/A>/ {... } to find lines with "</A>"

if ($var =~ /someExpression/ )
    {
    print "before match is >$`<\n";
    print "matched is >$&<\n";
    print "after match is >$'<\n";
    }

if ($var =~ /(part1)(part2)...(partN)/ )
    {
    print "first part of match is >$1<\n";
    print "next part is >$2<\n";
    etc.
    }

Also, re above
$var =~ s/(part1)(part2)/\2\1/; #reverses position of part1 and part2

\d \D [0-9] [^0-9]
\b \B start or end of a "word"
\s \S white space, all excep carriage return
\w \W "word" & not word

/^expression/ - at start of line
/expression$/ - at end of a line

A{5,10}, a{,10}, x{5,}
[0-9]
[0-9a-z]
[0-9a-z+-_]

a* a? a+ (abc)*

@list = split(/delimiter/,$line);
$line = join("delimiter",@list);
$line = join($glue,@list);

if $line =~ /matcher/i; # ignore case of letters
if $line =~ /$var/i;

$line =~ s/findThis/ReplaceWithThis/;
$line =~ s/findThis/ReplaceWithThis/g; #global
$line =~ s/findThis/ReplaceWithThis/i; #ignore case
$line =~ s/findThis/ReplaceWithThis/gI; #global & ignore case
 
if ($birds =~ /songbird|bluebird|redbird/)