Brain-Flak, 26 bytes

({<({}[{}])>{()<{{}}>}{}}) 

Try it online!

Outputs 1 for false and 0 for true.

Readable version:

({ <({}[{}])> { () <{{}}> } {} }) 

I originally had this:

{ ({}[{}]) { <>([()])<>{{}} }{} } <>({}()) 

Which is 10 bytes longer.

Brain-Flak, 26, 22 bytes

({<({}[{}])>{()<>}{}}) 

Try it online!

Outputs 1 for false and 0 for true.

Readable version:

({ <({}[{}])> { () <> } {} }) 

I originally had this:

{ ({}[{}]) { <>([()])<>{{}} }{} } <>({}()) 

Which is 10 bytes longer.

Brain-Flak, 26 bytes

({<({}[{}])>{()<{{}}>}{}}) 

Try it online!

Readable version:

({ <({}[{}])> { () <{{}}> } {} }) 

I originally had this:

{ ({}[{}]) { <>([()])<>{{}} }{} } <>({}()) 

Which is 10 bytes longer.

Brain-Flak, 26 bytes

({<({}[{}])>{()<{{}}>}{}}) 

Try it online!

Outputs 1 for false and 0 for true.

Readable version:

({ <({}[{}])> { () <{{}}> } {} }) 

I originally had this:

{ ({}[{}]) { <>([()])<>{{}} }{} } <>({}()) 

Which is 10 bytes longer.