Using Simple Patterns
To match a pattern (regular expression) against the contents
of $_, simply put the pattern between
a pair of forward slashes (/),
like we do here:
$_ = "yabba dabba doo";
if (/abba/) {
print "It matched!\n";
}The expression /abba/ looks for
that four-letter string in $_; if it
finds it, it returns a true value. In this case, it’s found more than
once, but that doesn’t make any difference. If it’s found at all, it’s a
match; if it’s not in there at all, it fails.
Because the pattern match is generally being used to return a true
or false value, it is almost always found in the conditional expression
of if or while.
All of the usual backslash escapes that you can put into
double-quoted strings are available in patterns, so you could use the
pattern /coke\tsprite/ to match the
11 characters of coke, a tab, and
sprite.
About Metacharacters
Of course, if patterns matched only simple literal strings, they wouldn’t be very useful. That’s why there are a number of special characters, called metacharacters, that have special meanings in regular expressions.
For example, the dot (.) is a wildcard
character—it matches any single character except a newline (which is
represented by "\n"). So, the
pattern /bet.y/ would match
betty. Or it would match betsy, or bet=y, or bet.y, or any other string that has bet, followed by any one character (except a
newline), followed by y. It
wouldn’t match bety or betsey, though, since those don’t have
exactly one character between the t and ...