Simple change of behavior or create new behavior:

#!/usr/bin/env perl

use strict;
use warnings;
use feature qw(say);

my $gizmo = frobnicate(
    sub { reverse split "", (shift) },
    sub { uc(shift) } );

say $gizmo->("nose");

sub frobnicate {
    my ( $foo, $bar ) = @_;
    sub { $foo->( $bar->(@_) ) }
}
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