Documentation for infix (<), infix ⊂ assembled from the following types:

language documentation Sets, bags, and mixes

From Sets, bags, and mixes

(Sets, bags, and mixes) infix (<), infix ⊂

Returns True if $a is a strict subset of $b, else False. More information, Wikipedia definition.

language documentation Operators

From Operators

(Operators) infix (<), infix ⊂

multi sub infix:<< (<) >>($a,$b --> Bool:D)
multi sub infix:<⊂>($a,$b --> Bool:D)

Subset of operator.

Returns True if $a is a strict subset of $b, i.e., that all the elements of $a are elements of $b but $a is a smaller set than $b.

say (1,2,3) (<) (2,3,1); # OUTPUT: «False␤» 
say (2,3) (<) (2,3,1); # OUTPUT: «True␤» 
say 4 ⊂ (1,2,3); # OUTPUT: «False␤» 

⊂ is equivalent to (<), at codepoint U+2282 (SUBSET OF).