Answer by
angille (55)
It is used to run regular expressions, following = to return true on a match and following! to return false on a match. Examples:
$foo = "string of letters";
$foo =~ /string/; # true
$foo =~ /other/; # false
$foo! ~ /other/; # true
$foo =~ s/ /_/g; # $foo is now "string_of_letters"
