In Sets, bags, and mixes§

See primary documentation in context for infix (<=), infix ⊆

Returns True if $a is a subset or is equal to $b, else False. More information, Wikipedia definition.

In Operators§

See primary documentation in context for infix (<=), infix ⊆

multi infix:«(<=)»($a,$b --> Bool:D)

Subset of or equal to operator.

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

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