Perl Regular Expression
Operators, or Functions

string =~ regexpr Is true if regexpr matches in string, which could be a constant or variable. 
while ($line=) {
    if ($line =~ /http:/) {
        print $line; # print URLs
    }
}
Alternately, using the default space $_ if =~ not used: 
while () {
    print if /http:/;
}
"split /regex/, string" splits "string" into a list of substrings and returns
that list. The "regex" determines the character sequence that "string" is
split with respect to. For example:
   $x = Calvin and Hobbes";
   @word = split /\s+/, $x; yields:    $word[0] = 'Calvin'
   $word[1] = 'and'
   $word[2] = 'Hobbes'
If the empty regex "//" is used, the string is s plit into individual characters.
If the regex has groupings, then the list produced contains the matched substrings
from groupings as well:    $y = "/usr/bin";
   @parts = split m!(/)!, $y;
   $parts[0] = '' # since first character matches!
   $parts[1] = '/'
   $parts[2] = 'usr'
   $parts[3] = '/'
   $parts[4] = 'bin'
Examples: