`OrderlessPatternSequence`¶

OrderlessPatternSequence[p1, …, pk] matches the block of k arguments at its position in any order:

$ wo '{MatchQ[{1, 2}, {OrderlessPatternSequence[2, 1]}], MatchQ[{1, 2, 3}, {_, OrderlessPatternSequence[3, 2]}]}'
{True, True}

The arguments it takes stay contiguous, so a match that would have to skip one fails:

$ wo 'MatchQ[{1, 2, 3}, {OrderlessPatternSequence[3, 1], _}]'
False

Names bind in the order the patterns are written:

$ wo '{3, 1, 2} /. {OrderlessPatternSequence[1, x_], ___} :> x'
3

OrderlessPatternSequence¶