"lc($str)"

Returns a lower-cased version of $str. The same as "CORE::lc()", but returns undef if $str is undef.

See "lc" in perldoc for details.

"uc($str)"

Returns a upper-cased version of $str. The same as "CORE::uc()", but returns undef if $str is undef.

See "uc" in perldoc for details.

"substr($str, $offset, $len)"

Extracts a substring out of $str and returns it. The same as "CORE::substr()", but returns undef if $str is undef.

See "substr" in perldoc for details.

"sprintf($fmt, args...)"

Returns a string formatted by the "CORE::sprintf()". $fmt must be a defined value.

See "sprintf" in perldoc for details.

"rx($regex_pattern)"

Compiles $regex_patter as a regular expression and return the regex object. You can pass a regex object to "match()" or "replace()" described below. The same as "qr//" operator in Perl.

"match($str, $pattern)"

Tests if $str matches $pattern. $pattern may be a string or a regex object.

Like "$str =~ $pattern" in Perl but you have to pass a regex object explicitly if you can use regular expressions.

Examples:

    : match("foo bar baz", "foo")     ? "true" : "false" # true
    : match("foo bar baz", "f..")     ? "true" : "false" # false
    : match("foo bar baz", rx("f..")) ? "true" : "false" # true

"replace($str, $pattern, $replacement)"

Replaces all the $patterns in $str with $replacements. Like as "$str =~ s/$pattern/$replacement/g" but you have to pass a regex object explicitly if you can use regular expressions.

"split($str [, $pattern [, $limit]])"

Splits the string $str into a list of strings and returns the list.