Sams Teach Yourself Perl in 21 Days, Second Edition

Pattern Matching Operators and Expressions

Let me first start with a quick overview of the regular expression information I've already covered. To construct patterns that search a variable for a particular expression, you use two operators: the regular expression operator m// and the pattern-match operator =~, like this:

if ($string =~ m/foo/) {
   # do something...
}

As you know, that test simply checks whether the variable $string contains foo.

For these sorts of patterns, the m is optional and can be left off (and usually is). In addition, you can leave off the variable and the =~ if you want to search the contents of the default variable $_. Commonly in Perl, you'll see shorthand pattern matching like this one:

if (/^\d+/) { # ...

Which ...