Documentation for method contains assembled from the following types:

class Str

From Str

(Str) method contains

Defined as:

multi method contains(Str:D: Cool:D $needle --> Bool:D)
multi method contains(Str:D: Str:D $needle --> Bool:D)
multi method contains(Str:D: Cool:D $needle, Int(Cool:D) $pos --> Bool:D)
multi method contains(Str:D: Str:D $needle, Int:D $pos --> Bool:D)

Coerces the invocant (represented in the signature by Str:D:, that would be the haystack) and first argument (which we are calling $needle) to Str (if it's not already, that is, in the first and third multi forms), and searches for $needle in the invocant (or haystack) starting from $pos characters into the string, if that is included as an argument.

Returns True if $needle is found. $pos is an optional parameter, and if it's not present, contains will search from the beginning of the string (using the first two forms of the multi).

say <Hello, World>.contains('Hello', 0);   # OUTPUT: «True␤» 
say "Hello, World".contains('Hello');      # OUTPUT: «True␤» 
say "Hello, World".contains('hello');      # OUTPUT: «False␤» 
say "Hello, World".contains('Hello', 1);   # OUTPUT: «False␤» 
say "Hello, World".contains(',');          # OUTPUT: «True␤» 
say "Hello, World".contains(',', 3);       # OUTPUT: «True␤» 
say "Hello, World".contains(',', 10);      # OUTPUT: «False␤»

In the first example, coercion is used to convert a List to a Str. In the 4th case, the 'Hello' string is not found since we have started looking at the second position in it (index 1). Note that because of how a List or Array is coerced into a Str, the results may sometimes be surprising. See traps.

class Cool

From Cool

(Cool) method contains

Defined as:

method contains(Cool:D: |c)

Coerces the invocant to a Str, and calls Str.contains on it. Please refer to that version of the method for arguments and general syntax.

say 123.contains("2")# OUTPUT: «True␤»

Since Int is a subclass of Cool, 123 is coerced to a Str and then contains is called on it.

say (1,1, * + * … * > 250).contains(233)# OUTPUT: «True␤»

Seqs are also subclasses of Cool, and they are stringified to a comma-separated form. In this case we are also using an Int, which is going to be stringified also; "233" is included in that sequence, so it returns True. Please note that this sequence is not lazy; the stringification of lazy sequences does not include each and every one of their components for obvious reasons.